The Science of Sensitization (or How in the World We Become Allergic…)


A few months ago, I talked to you about The Science of Anaphylaxis.  We started our exploration of an allergic reaction with a mast cell that had IgE antibody to a food allergen on its surface, learned how allergic reactions are initiated, and ended the conversation with the signs, symptoms, and treatment of anaphylaxis.  But how did the mast cell get that IgE antibody to a specific food on its surface in the first place?  How did the mast cell get primed, so to speak, for an allergic reaction?  How do we become allergic?  Well, we become allergic through a process called sensitization.  So here, my friends, is the foreword to The Science of Anaphylaxis, it is The Science of Sensitization.  We will discuss in depth one of the ways that an individual can become allergic.  I think you are ready for this, but just like the last science post, you may need to read it a few times.  (I had to write it a few times!)

Okay, here we go.  When an individual eats a food, (let’s use peanut as our example again), it enters the gastrointestinal (GI) tract and begins to be digested.  At some point during this process, the tiny peanut protein passes through the wall of the GI tract.  Through a series of events, the protein finds its way to cells in the blood stream and lymphoid tissues.  This is where the peanut protein stumbles upon a type of cell called an antigen-presenting cell.  Antigen-presenting cells do exactly that – they present (or show) antigens (allergenic food proteins, for example) to other cells.  An antigen is a foreign substance that initiates an immune response by the body.  This immune response usually includes the creation of antibodies that help to rid the body of this foreign substance.  Many types of cells can act as antigen-presenting cells.  In this example, the antigen-presenting cell will be a B cell.

When a B cell (seen in blue in the figure below) encounters peanut protein, it takes the protein from the outside and internalizes it.  It processes the protein and then puts it on a molecule that resides on the surface of its cell (see the B cell with peanut protein on its surface molecule below).  The peanut protein on the surface of this B cell will then get presented to a T cell (shown in green).  Believe it or not, this T cell has on its surface a peanut-specific receptor, as well as receptors for so many other proteins.  When this receptor on the T cell sees this peanut protein on the surface of the B cell, the cells realize that they have something in common and they begin to communicate.  The conversation between the B cell and the T cell is intense and complicated. There is an automatic connection between them.  They come into contact with each other’s surface molecules and engage in other receptor-based physical interactions.  They also spew out cytokines (chemicals) as another way to converse with each other and boy, do they have a lot to say!  The T cell specifically releases IL-4 and IL-13 and these cytokines cause the B cell to undergo several changes.  These changes eventually lead to its secretion of peanut-specific IgE antibody represented by the blue Y’s in the figure below.  (IgE stands for immunoglobulin type E.  It is a type of antibody that aids in ridding the body of parasites and plays an important role in allergic reactions.)

This is tough.  Try picturing the B cell and T cell in the figure above like two people.  They meet each other in the middle of a huge crowd and they have instant chemistry. They recognize something in the other person that they are attracted to.  They share a good handshake, a strong hug.  They have a common interest in food.  They talk easily.  They effortlessly exchange information. Their interaction ultimately is so powerful that it changes their lives forever.  This is romantic stuff.

Now back to the science… we left the B cell churning out peanut-specific IgE antibody while under the influence of IL-4 and IL-13.  It has the ability to secrete antibody specific to whatever food protein that it originally encountered.  It could be egg, wheat or cow’s milk, for example.  Remember from The Science of Anaphylaxis that an antibody looks like an arm with a hand on the end (shown in blue and attached to a mast cell in the figure below). These peanut-specific IgE antibodies are now flowing in the blood stream in an attempt to find and bind to high-affinity (very sticky) IgE receptors on mast cells.  These IgE receptors on mast cells are perfect, sticky landing pads for the circulating IgE antibodies.  When the peanut-specific IgE antibodies bind to the IgE receptors on mast cells, this marks the completion of the process of sensitization.

The process that I described occurs in atopic individuals (those with a propensity to become allergic).  In the case of these allergic and now-sensitized individuals, once the mast cell has the peanut-specific IgE attached to its surface, it is primed for a reaction the next time the peanut protein appears in the body.  This means that the next time a peanut-sensitized individual encounters a peanut, the signs and symptoms of an allergic reaction or anaphylaxis can occur.

Now I am going to confuse things a bit but only in hopes of answering some questions that may have come up for you.   It is good to keep in mind that the process I have described does not end in sensitization in non-allergic people. An individual without a genetic predisposition to allergy will likely undergo what is called, tolerance, instead.  They will have similar cellular communications that result in that individual’s ability to safely eat (tolerate) a potentially allergenic food.

Imagine it like this…  When two people meet, there is a better chance that they will simply and happily co-exist with each other (or tolerate each other) than there is a chance that they will instantly hit it off.  These two people may exchange small talk but they do not cause a radical change in the lives of one another.  They don’t move the other one into action.  Tolerance is what normally happens.  Allergic sensitization is the exceptional response.

You should also know that there are some individuals who undergo sensitization but do not react the next time their cells encounter the allergenic food. They are not clinically allergic.  See, I told you this was confusing!  These individuals go through this process but do not react to foods. This group of individuals is fascinating and likely holds a key piece of information in the search for the treatment or cure of food allergy.  I mention this in order to teach you that not every positive blood test indicates that an individual will have an allergic reaction to that food.  So think twice before you ask your physician to draw extensive “panels” of blood tests (food specific IgE antibody levels, also referred to as RASTs or ImmunoCAPs) to foods that there is no history of a reaction to in order to diagnose food allergies.  This practice can lead to an over-diagnosis of food allergy and thus, an unnecessary over-avoidance of food.  It can also lead, perhaps, to the avoidance of food that the person was eating safely just the day before.

I hope that piece gives you a deeper understanding of how some of us become allergic.  I have left many of the nitty-gritty details out of this explanation because it is simply not easy material, but I am confident that you will be able to get the big picture. If you want to work through this whole story, read this post and follow it up with The Science of Anaphylaxis.  It will bring the allergic puzzle together for you – sensitization followed by allergic reaction.

Please share this post with your friends!  Even if they don’t have food allergies, the process of sensitization is basically the same for those people who are allergic to pet dander, tree pollen, ragweed or other environmental allergens. And we all know someone who is sneezing and rubbing their eyes as spring draws to a close and summer grass pollen fills the air!

Please sign up for email updates to the right, if you haven’t already.  Also, if you so desire, follow The Allergist Mom on facebook and twitter – links can be found on upper right of site in the little gray circles!  Thank you!

This entry was posted in Observations, Science. Bookmark the permalink.

59 Responses to The Science of Sensitization (or How in the World We Become Allergic…)

  1. Paul B says:

    Wow! You actually were listening in those lectures I had to give when you were a fellow at Northwestern!

    Great to see you throw in the confusing story of sensitized people who don’t react…it’s those people we are trying to get funding to study at NU, because if we can make people with allergies a little more like them, we should all get along just fine!

    • Sarah says:

      Getting this comment from you means the world to me. When I pressed “publish” on this post, I actually said to myself, “I hope Paul thinks this explanation is a good one.” Thank you for teaching me so well… so that I can teach others. What a gift. Thank you.

  2. Kim says:

    Thank you! I have a son who was diagnosed before he ate solid food. He was 6 months, I was breastfeeding and he had horrible eczema, breathing issues and spitting up. He has tested positive (blood and scratch) 2x for peanut, dairy and egg, added soy this year. He’s almost 2. Based on what I’ve read here, woud you suggest food challenges to the foods he’s tested positive for in an allergists office? He still has awful eczema and we obviously avoid his known allergins.

    • Sarah says:

      Thank you for reading! Your allergist is probably looking at the combination of blood and skin tests as well as history to determine when food challenges should be offered. Unfortunately, I can’t specifically comment on what should be the next step in your son’s allergy management plan, as I am not his physician, but I think you ask a very good question that you should present to your allergist. You are now armed with a little more knowledge so use it to feel confident to start a conversation with your physician!

  3. Kristen says:

    I had ImmunoCAP testing done on my 3 year old son who came up positive to the skin test for peanuts and cashews. I was of course hoping that his IgE markers would not be as high as his skin test predicted. However, the IgE markers that are correlated with anaphylaxis came out high and the doctor said that I should EpiPen him immediately if he ingests peanuts as he is at such high risk for anaphylaxis.

    In reading your extremely informative and user friendly article it seems like the immunoCAP findings may not correlate with an actual anaphylactic reaction. He has never had peanuts so I am not sure what his actual reaction would be. Can you comment on the ImmunoCAP testing and risk for anaphylaxis in this case a bit more? Dont worry, it wont make me drop my guard about carrying an epipen and avoiding peanuts like the plague. Im too neurotic for that.

    • Sarah says:

      I wish there was a way to tell us which people have positive blood tests and react, and those that have positive blood tests and do not react. Right now, besides a physician-monitored food challenge, there really isn’t any other way to determine which group an individual would fall under. Also the ImmunoCAP values do not in general tell you how severe a reaction will be either. Allergists must take into account skin tests and blood tests as well as history and reactions to determine a plan for each patient. I wish I could give you more specific advice/thoughts for your son but without being his physician, I really do not have all the information that I need. I would recommend taking your new knowledge and asking your allergist these excellent questions and hopefully he/she can answer them in a way that is specific to your son.
      Thank you so much for reading and for your comment!

  4. Diana says:

    I also find those positive RASTs with no symptoms fascinating and I wonder if that’s going to turn out to be the case with my daughter and nuts. She has tests with confirming reactions for all her other allergens, but has never reacted to nuts. She’s never been given them, but I find it hard to believe she’s never been cross-contaminated seeing as we’ve had cross-contamination problems with almost everything else at least once. (Our allergist doesn’t recommend removing her allergens from our home.) She’s only 20 months, so time will tell and someday we’ll do a food challenge.

    Thanks for sharing all your knowledge!

    • Sarah says:

      You’re welcome! Physician-supervised food challenges are about the only real way to know for sure, you’re right! What a love/hate relationship we all have with those… And I guess there is no real way to know if she has ever had contact with the nuts through cross-contamination or not though. I keep my kitchen virtually allergen-free (except for pre-wrapped items I send to lunch for my non-allergic son) but now I am curious what other readers do in terms of allergen-riddance in the home? Love to hear comments on that.
      Thank you so much for reading, Diana! I appreciate your comment. Have a wonderful night!

      • Diana says:

        Our original allergist had us keep peanuts totally out of the house, but we switched pediatricians and she was not thrilled with our first referral. She referred us to a doctor at Hopkins, and he told us we could bring them back in. One thing that stands out to me in reading the comments (and that the allergist asked about before giving me the go ahead) was that I have no other toddlers or preschoolers in the house. My other children are 11 and 8 and fully understand the measures they need to take to keep our little Bee safe. Also, from what we’ve experienced, she has to have a large amount touch her skin or actually ingest her allergen in quantity before her reaction goes into hyperdrive. That’s how we found out she was allergic to kiwi. She had had small amounts and been fine, but when I gave her a whole kiwi the hives were everywhere, and she was as close as she’s ever been to anaphylaxis.

        • Sarah says:

          Definitely agree with you that the age of the children in the household is very important in deciding whether or not to keep allergens in the home. Great point to bring up! Thank you for sharing.

  5. Linda says:

    Very interesting article! I have a daughter who is allergic to peanuts and tree nuts(at least that’s what the blood and skin tests say). She used to come up positive for a good number of other foods including dairy. I have seen her have a reaction to dairy that Benadryl stopped thankfully! That came after discussions with her dr about all of her eczema and upset tummy when I started her on table food. She as never been exposed to peanuts or tree nuts since I saw her tendency towards allergies so early on. My son had allergies to dairy, wheat and eggs, but grew out of them. My husband is a very sensitive person and cannot eat certain foods without feeling bad(he also has Crohn’s) He has had allergy/sensitivities testing and many came out positive). He avoids some of them, but not others.
    As far as keeping allergens in my home, I have nothing that contains peanuts or tree nuts in my house. I do have cereal that has almonds in it since my daughter does not test positive for them(she doesn’t eat it though). I only keep ingredients for baking/cooking etc that are safe for her. She is 9 and questions me on many things that I make before eating them. I know she won’t eat anything that she shouldn’t, but I’m afraid of cross contamination or me mistakingly using an ingredient that isn’t safe.

    Thank you for the article! Very interesting. I haven’t read the science of anaphylaxis yet. The thought of it upsets me so much, I can’t get myself to read it.


  6. Elizabeth says:

    Wow! I just found your blog and it is amazing! Thanks so much for sharing. I am also curious about whether people keep their homes allergen free. My 4-year-old daughter is allergic to peanuts. We’ve suspected it for a while because she had such a strong dislike for anything with peanuts in it and would spit out immediately, but found out for sure about 8 months ago. I have only just discovered all the possibilities for cross-contamination (Asian food, baked goods, etc.) and it is definitely overwhelming!

    • Sarah says:

      I am so happy that you found my blog! Thank you for reading it and for your comment! We all choose the way that works best for us and our families in terms of allergens in the house. I definitely do not cook with any of ours (meaning our kitchen is top 8 allergen-free plus some) but for me, it is worth this extra effort and creativity. I feel a lot less anxious in my house and am happy to provide a safe-food space for my kids. I will keep certain allergen-containing foods that are packaged, i.e. cheese sticks, in high cabinets/shelves in our house to give to the children who are not allergic when they are leaving the house or in a special area we have set aside in the house for eating allergen-containing food… over a plastic, disposable tablecloth.:)
      Thank you again!

  7. Tricia says:

    I love this explanation. You did a great job explaining the differences between being only sensitized for an allergen and being truly allergic.

    My children have multiple food allergies and they are the real deal. Each child has some allergens that his brother doesn’t, but we try to avoid all foods in the home that either one is allergic to. We have had accidents where a baked good made it into the house and ended up in the hands of our egg allergic toddler. Fortunately, we stopped him before he took a bite. As a food allergy parent, I prefer keeping our home an allergen free zone for the piece of mind it brings. It’s easy once you get used to it. I’ve learned to bake without eggs and we actually like the taste of Sunbutter better than peanutbutter.

    • Sarah says:

      Thank you Tricia! I appreciate your comment about both the post and how you deal with food allergens in the home. It is something that everyone does a little differently but I think it is helpful for people to hear what others are doing!
      Thank you again and have a great day!

  8. Judy says:

    Thank you for the science aspect of allergies! I have a 4 y/o PN/TN allergic son and a 6 year old non-allergic. We have recently relocated from SW suburbs of Chicago to NC where nut trees are prevalent and have only had one incident here where my son’s lips swelled after playing outside, possibly with squirrel cracked walnuts, at preschool, but otherwise, have experienced no known reactions. Based on a combination of all of his test results from a year ago in Chicago, however, he’s not eligible for an oral challenge at this juncture.

    In response to your curiosity of allergen-riddance in the home, here’s what we do/don’t do:

    We don’t allow consumption of PN/TN in/around our home. We often have nut containing Kind or Clif bars in the house, literally locked away in a high cabinet for my husband to take to work and eat there (not in the car, etc). My non-allergic son can consume peanuts/tree nuts at his friends’ homes (the parents love this opportunity to spoil him), followed by appropriate hand washing and teeth brushing an hour or so before he sees his little brother. When we have kids over for play dates, I shuffle them into the bathroom to wash their hands with soap and water before they play. Our new friends have become so supportive and sensitive to our routines that they ask a lot questions and help by bringing safe foods. If something ‘unsafe’ makes it’s way here in the arms of friends, we offer huge apologies, encourage them to take it home with them when they leave and thank them for their efforts and understanding.

    I look forward to hearing what others do to keep their homes safe.

    • Sarah says:

      Hello Judy,
      Thank you for sharing your allergen plan for the home. Sounds nearly identical to ours! Works for us! I am glad that you enjoyed this post, thank you for your comment.
      Have a wonderful day!

  9. Debra says:

    There are some times when I barely know somebody, but I feel like they did something so wonderful for me that I want to say I love you. Well, I usually hold back, but I will not this time, because this is the second time you made me feel like this, I love you! Thank you so much for teaching me and making it so easy to teach others who otherwise just wouldn’t get it. You are making visible what some people try to ignore even exists. What a love you are spreading! If you ever make a booklet out of these I plan on buying a bunch and handing them out to loved ones or any in doubt. For now I am going to share my copy and post on Facebook.

    • Sarah says:

      Well, I love you for telling me that! That is so kind of you. I really appreciate your comment – to know that these posts are helpful to you means so much to me. Thank you!! There may be a book in the future that will contain these explanations. I’ll let you know if I do it!
      Thank you again. You made my day.

  10. Chris says:

    This is Killer – Thank You – A book please would be great! Your blog is the best resource for food-allergy families on the Web, not to mention eloquent, intelligent, witty and artistic. So please write as often as you can!

    I see many comments above about how allergen-free folks keep their homes, so I will weigh in as well. One of our children is very allergic to peanuts and several tree nuts (4 anaphylactic reactions in 4 years). To assure him (and our caregivers) a safe place where he can eat or pack anything without worry , we keep our home nut-free (or as free of nut protein as possible, given the state of food labeling laws). We filter out anything (a) made in a facility that also processes any foods containing nuts, (b) made on shared equipment even if with “good cleaning practices”, or (c) made in a manner that I cannot verify. Mistakes are just too real for me, whether due to sitters or visitors, or our own errors when we are too tired to find our glasses to read the entire label, so we just try to ban nut protein entirely. We all rest more easily because we believe that we have reduced our risks to manufacturer errors in labeling, or plant operations that just do not match the disclosures, or handling that resulted in nut protein on the outside of the package. Fortunately, I’ve been able to source a “safely” made food/ingredient for most of our needs, including ethnic items, and “workarounds” are now becoming second nature. Thank goodness it’s just peanuts and tree nuts for us presently – I can only imagine the undertaking at your home!

    Thanks for sharing your literary and educational gifts with us!

    • Sarah says:

      Thank you so much for your way too kind comment. It means the world to me! Thank you also for sharing what works for you in your home. Everyone sees things a little differently and I am happy to see everyone sharing what works for them in a nonjudgmental way, refreshing. I am on the same page as you in terms of keeping the house a place where we can all take a little breather… works for us! :) Thank you again!

  11. Andria says:

    What about the component of vaccinations being the avenue of the protein entering the blood stream?

    • Sarah says:

      Good question, Andria. There are many possible ways that people think you can be sensitized – through the gut, through the skin, through the airways. There is a possibility that one could be sensitized by a protein found in a vaccine but I think this would be a very rare occurrence, considering how many children are vaccinated. As a pediatrician, I wouldn’t recommend skipping vaccinations to avoid becoming allergic to the components at this point. There are not enough data to support that. You are thinking though!!

  12. Sondra P. says:

    Thank you , again, Sarah for helping me understanding on a deeper level the crazy, confusing world of allergies. Your explanations are helpful on many levels. In our home, our 4 yr old daughter has no known allergies, and son 2-1/2 yrs old has multiple food allergies. He was diagnosed at 6 months old after he had a contact reaction (hives and rash) after I touched him while eating almonds. He has gone through two rounds of testing in two years and has shown positive skin and rast test results to peanut, tree nuts, wheat, egg, sesame, soy and, now multiple legumes. The only food (out of these that he has eaten) has been a chickpea of which he experienced a very severe reaction. We avoid all of his allergens, and he has met all of his growth/developemental milestones. He is thriving and doing fine. We maintain an allergen free household, with the exception of wheat. I do keep bread in the house in the freezer for my daughter and husband; they dont like the GF kind. My question is this…Since my son never ate these foods prior to his first reaction, how is he allergic? Genetic? My husband and I have mild, seasonal allergies, but no food allergies. Also, is it rare for someone to have so many food allergies (including multiple legumes)? I am hopeful that our son will outgrow some of his allergies, (our allergist has maintained that the nut allergies will likely be lifelong, but I would love for him to have a wider range of food). At what age do you generally see young ones starting to outgrow allergies?
    Thank you again.

    • Sarah says:

      I am so happy that this explanation helped you to understand this part of the allergic reaction better. That is exactly why I do this. You really do have to “see” the food to be sensitized. Is it through breast milk, in utero, through an unknown cross-contamination event? Not exactly sure but likely the cells have seen this food at some point. It is not usual to have so many food allergies but it absolutely happens. My son has had severe allergic reactions to every legume he has ever eaten. There is not a magic age that we see people lose their sensitization to foods. We used to see a great number of children do this before school age but studies show children keeping their food allergies for longer. I wish there was a better answer. Thank you so much for your comment and for continuing to read!

  13. Jenni says:

    Very interesting article! Thank you for writing! Curious how this scientific process is different or explained in people with delayed responses. Both my kids have multiple food allergies but their reaction is very delayed, up to about 7 days. And I’m fairly confident they are not mis-diagnosed because they test allergic to blood and scratch testing and we have done elimination diets. For example, I had my youngest son on strictly an amino acid based formula for months because he was previously covered in eczema and vomitting daily. After a couple weeks of only the amino acid formula we had no eczema and no vomitting. We stuck to that diet a couple more months and then slowly introduced dairy. For the first 6 days he was fine. Then, on day 7 the eczema started and on day 8 the vomitting. This went on for days after stopping the dairy, but again, after getting it out of his system and just having the amino acid formula, he was good again. I am curious if the science of these delayed reactions is compeltely different.

    • Sarah says:

      Thank you for your comment and question. I can’t comment on the exact mechanisms of the reactions experienced by your son, but in general, the science of delayed reactions is different from the science of IgE-mediated reactions. IgE-mediated reactions are immediate reactions – by definition. There are other types of reactions to foods (ie. FPIES) that can take more than a few hours to develop. I have seen food contribute to worsening eczema after days of ingestion but likely this mechanism is distinct from the IgE-mediated type of reaction. It instead may be moderated more by T cells.
      Hope this helps!

  14. Stacey says:

    We seem to be in the minority here. :-) We are a family that keeps allergens in the home. DS is 4, has had ana reactions to dairy and egg (contact reactive to egg also), has FPIES to soy, and Immuno-cap tests extremely high to peanuts and moderate to several tree nuts. He has never eaten any type of nut, but because of his history of reactions to other foods that he tests high for/has reactions to, his allergist suggests we steer clear of nuts at this point.

    We have a cabinet on one side of the kitchen that is all “safe” food. He cannot reach this and has never tried. We also have a snack drawer with only safe foods, so he and our 6 yr old can get snacks, after they ask. We have not had an issue with cross contamination in our house, not even once. All four of us are very aware of his allergies–and we all watch out for him. I cook a main meal using all safe products, but then garnish with appropriate foods for each person eating.

    When our son was diagnosed with FPIES at 14 weeks, our daughter was two. At that point we had no idea what he would react to in the FPIES world. There was–and still–is no real testing other than food challenges for FPIES. We did not want to take an entire plethora of foods away from our 2 yr old. Little did we know, he would start having ana reactions at 12 months to atypical FPIES foods. We had no idea you could have FPIES and IgE allergies. Ha! We decided that for our home, we would keep our son safe while also allowing our daughter some sort of normalcy. Now, our life revolves around our son–what restaurants we can/cannot go into, wiping everything down constantly, where we can travel, what hotels we can stay in, MANY doc appts, and many conversations revolve around him–at home and because of the curiousity of others. My husband and I feel it is very important for our daughter to feel emotionally safe, just as our son must be physically safe. Many times our daughter has said “everything is about AJ” and sadly, many times things ARE about AJ. They have to be. I also feel this way regarding my husband. He was raised in the South by a mother that cooked to show her love, therefore he knows how to receive love through cooking. This is the reason we have chosen not to take allergens out of our home. At this point, it is not necessary to do–for our family. This is just how we are in OUR home–and I have no judgement at all towards families that take the allergens from their homes.

    We often eat “safe” meals, make “safe” baked goods, eat SO much healthier now because we eat mostly whole foods. But until I NEED to, I refuse to pull the foods my husband and daughter love. If our son did not do well emotionally with others eating things he cannot, I would probably feel different. I am blessed that he understands what egg and milk do to him–he remembers the failed baked egg challenge, the many blood draws, the IV’s required for FPIES food challenges. Our little man has been through a lot–and will tell people that ask about his MedicAlert bracelet “I wear this because I’m allergic to xyz and it makes me puke up everywhere and ride in the ambulance.”

    Sorry for writing my own blog entry. :-) Just wanted to give the perspective from a family that does have allergens in their home.

    • Sarah says:

      Thank you for your blog post ;) Seriously though, thank you for sharing this with our community. This is one of the things I really enjoy about the community we are building here – I do believe that we are all understanding and nonjudgmental of the way the other families manage food allergies in their life/home/school etc. When you mentioned about how your daughter sometimes feels like everything is about her brother, it struck a chord. Sometimes the siblings with no or fewer allergies do indeed feel a little left out, like they are getting a little less attention. It is such a balancing act. Thank you again for reading and commenting!

  15. Great article! Having gone through the atopic march and coming out with multiple allergies of all kinds, I’ve heard and read many explanations, but found your post much more thorough and very easy to understand for someone without a professional medical background. I love your blog in general because you share information that is compassionate, accessible and scientific – a perfect mix. Thank you!

    • Sarah says:

      Thank you, Tristan! That means a lot to me that you felt this explanation was easy to understand and accessible. That is very important to me. I appreciate your comment and kind words.

  16. Diana says:

    That was great….a very complex matter broken down for us. My son has peanut/tree nut allergies but we have just self-diagnosed him with a fish allergy within the past couple weeks. We’ll be taking him back to the allergist for testing soon….sigh.

    • Sarah says:

      I am glad that you enjoyed this post! Bummer about having to go back for another possible allergen. You’ll manage it as well as the others though, if it is confirmed. Let me know if you need anything.

  17. Laura says:

    You really know your stuff! I find your blog so helpful.
    Because of your more than usual amount of knowledge on these things, I’m wondering if you’ve heard about what we’re dealing with and can point me towards how I might get an explanation from our allergist.
    Our 10 month old son is allergic (seemingly anaphylactic as he had swelling/hives and hives/wheezing and hives/vomitting) to milk and eggs. Fairly typical reactions.
    The problem I am having in getting a better understanding of how his allergies manifest lies in the fact is that he had consumed milk formula for two weeks on and off (and then for three days straight) before the first reaction (edema and hives). I had been exclusively breastfeeding prior to an out of town excursion that did not allow for me to be present all the time (hence the formula) and had consumed mass amount of dairy and he had no reaction prior to that time – no eczema, etc. We obviously stopped giving him formula after this incident and I eliminated milk from my diet in all forms.
    Then, a month later, our doctor had us give him formula to confirm milk allergy and he had no reaction. I had studied up on all the symptoms, and there was nothing – no drooling, stomach issues (diarrhea, etc.), skin swelling – nothing. I suppose he could have had an impending feeling of doom, as I can’t ask him, but nothing I could see. Happy as usual.
    Then, a week after that, I gave him formula again and he had another reaction (hives/wheezing). He tested positive (small wheal) on a skin prick test.
    With the egg allergy, he had scrambled eggs at least 6 times over a month period, and had baked cake with eggs. Then, last week, he had scrambled eggs and developed hives and vomitted.
    So, I’m confused as to why he is having these reactions after multiple exposures. We are meeting with our allergist soon about the egg, but he didn’t have a clear answer about the random milk reactions the last time (maybe I wasn’t asking the right questions), so if you could give me the right questions to ask about the process?
    I’m afraid to feed him anything at this point considering he could react after any amount of times having consumed it safely.
    Sorry for any rambling – thanks so much for any insight you may have!

    • Sarah says:

      I am unable to give you personalized medical advice regarding your son without seeing him as a patient but here are my thoughts about situations like this. I wish I had a good explanation for children who seem to lose their sensitization and then quickly become sensitized again. I had similar experiences with one of my sons. For example, he tolerated chicken for a certain amount of time and then he would react. We would wait a year, try it again. He would tolerate for a few weeks and then start reacting. The only explanation that we could think of is that he was being re-sensitized rather quickly to that food. There is a possibility that giving the food intermittently actually increases the chance of being allergic and that perhaps being exposed to it every day or more often while he is tolerating it may keep the sensitization at bay. This is speculation only. You may consider asking you allergist questions along this line of thinking… This is a tough situation to get a real clear picture of. Hope this helps a little.
      Thank you!

      • Laura says:

        Thanks, Sarah! Your background is a great starting point for me to bring to our allergist for our situation. All the best to you and your family.

  18. Tanya says:

    We have multiple food allergies in our home. 3/4 of us have celiac and are gf, 2/4 are dairy free, and 1 is FPIES to fish/shellfish. We do not have any fish/shellfish in our home nor do we allow an others to bring it in. I allow gluten and dairy in the home, but I am careful about it. We have dedicated equipment for gf only use. We are careful dependent upon the reaction. I also have friends that come that are allergic to nuts and peanuts and we clean everything thoroughly before they come. I cook gf/cf/fsf every day but I have a daycare and don’t make them all be allergen free. I just have them sit at a different table and wash them well before they get down. I think that it is important that my kids learn to be safe in a “normal” environment as well so that they don’t get too used to everything automatically being safe. We also have lots of safeguards for school to keep them safe. It’s a juggling act that changes as they get older and more able to care for themselves. My kids will always have these allergies and I feel that they need to adjust to the rest of the world not always being safe for them. That being said, I do try to make their home as much of a safe haven as I can. I don’t allow their previous favorites and I don’t buy them for the other kids. They deal with it all day, they shouldn’t have to at home.

    Thank you for the explanation. I have to constantly explain the difference to others regarding their various reactions as they are IgE, T-cell, and autoimmune reactions. The response is different for all of them and it gets a bit confusing for others. I just ask them not to feed the kids (or me!) lol!

    • Sarah says:

      I appreciate you sharing how your household runs in terms of allergens. It does become quite a juggling act when your children, or you and your spouse, have varying food needs/restrictions. It sounds like you have managed to figure out a way that works for your family. Must’ve been a lot of work!
      You’re welcome for the explanation. I am hoping to get one out about FPIES at some point soon. The science posts do take a bit of time but if you can be patient with me, I’ll try to get that to you!
      Thank you, Tanya!

  19. Charl says:

    Sarah, you commented to Diana that you would love to hear from others about how they handle allergy-riddance in the home. We use a Heppa filter to control the oak pollen our child is so allergic to and dust/vaccum regulary. The Rainbow vaccum collects all the pollen/dirt in the water and we can change the water with each room we vaccum (just dump it out on the garden). We grow a lot of our own vegetables and herbs (no pesticides or addatives) and make our own compost from the rinds, etc. We have a blender and juicer to make our own foods as fresh as possible. Our allergist recommended a 4 day rotational diet in addition to avoiding the multiple food allergens our child is allergic to. After a very scary skin test, we purged the kitchen of all the “no-no’s” (friends and neighbors benefited). Then we dedicated a shelf in the pantry for “Day 1 foods”, posted a list of what can be eaten that day and placed a colorful folder on the shelf to hold recipes for just those foods. We did this for Day 1, Day, 2, Day 3, and Day 4 and marked the calendar on the refrigerator to correspond with the 4 day rotational pattern. Taping a star on the shelf being used for the day helped make the family independent (did not have to call Mom constantly to ask “What day are we on ?) Now we have modified recipes so we can make cookies or lunches, etc. for each day while getting a wide variety of nutrients directly from foods and not having to rely on vitamin supplements. Our child attends a school that lets us pack our child’s lunch and snacks and keeps the Epi-pen and rescue inhaler in the school’s office. I teach my child’s Sunday School class and use vacation time to attend school parties so I can help clean the tables, etc. so he has less exposure to potentially hazardous allergens in both food and non-foods.
    We have explored a wide variety of grains, oils, vegetables, and meats. Dr. Sally Rockwell has a good cookbook that explains how to do this and there are some good resources on the Internet, too. Hope this information helps someone as much as it has helped us. We now have a much healthier child and healthier family. (And, yes, my husband and I work full-time, too, and do our own housework, etc.) God bless.

    • Sarah says:

      Charl, Thank you for your comment. I am not very familiar with what you mean by the 4-day rotational diet. Is this a means to prevent sensitization? I am glad that it worked for you. Just this year, I planted a bunch of my own veggies and herbs, strawberries too and the kids and I have been enjoying this immensely. Food allergies hasn’t brought us all that much joy but the way we eat now because of it brings us great joy. Thank you for sharing.

    • misty says:

      hi charl,

      we are on a 4-day rotation diet as well, but i seem to be struggling with it far more than you! would love your email address or any resources you have used to implement the diet. we are celiac with soy and dairy allergies as well.

      thank you!

  20. Hi
    I really enjoy how you wrote about this subject. My son this day last year went into anaphylactic shock after coming into contact with peanuts. we are not sure if he ingested it but still it was a frightening moment.
    I want to comment on the advice you give about blood tests etc… I agree with you. The Dr tested for peanuts, almonds, Hazelnuts and eggs and they all came back with a raised IgE level. However he has and still does eat nutella with no problem. He cannot touch raw egg but baked egg is ok for him.
    Anyway it is a roller coaster of a ride with a child like that but as his parents we have learnt how to be cautious, careful and how to roll
    with it. And to date he has had a good year. Some heightened moments but nothing like last year.
    Thanks for your blogs, advice and all that you share.


    • Sarah says:

      Thank you for reading and for your comment. The anniversaries of reactions bring back so much emotion. I am very happy that this has been a better year for your family! Being able to “roll with it” is such an important attitude to have, it really helps everyone! Thank you, Suzanne!

  21. Rachel says:

    Hi Sarah,
    Thank you for this wonderful post. I am so impressed by your ability to connect with people and the way in which you make complex ideas easy to digest. The diagrams and metaphor really helped explain something that puzzles allergic and non-allergic people alike.

    • Sarah says:

      Thank you very much for this comment. It means so much to me. I will be in touch with you soon!

  22. Cindy in GA says:

    If the peanut allergy is eventually outgrown (or desensitized), do the mast cells no longer have the peanut-specific IgE on the surface? If so, how does desensitization make that happen? Is anything known about the differences between those who outgrow the allergy and those who don’t?

    I know those are big questions – and maybe no answers are out there yet. The hope of outgrowing keeps me wondering about how that might happen.

    Thank you for sharing your wisdom and experience here!

    • Sarah says:

      These are big questions! I think I may have to write another blog post about tolerance and desensitization to answer this fully! It is possible to have some peanut-specific IgE show up on blood tests but no longer react. You can still actually have positive skin prick tests and be able to tolerate the food. Nothing is really 100%. We don’t know enough about the difference between those two groups of people yet but I know of some papers in the works that are looking more deeply into this. Be on the lookout for another science post that will go into your questions a bit deeper but hopefully this is a start!
      Thank you for reading and for your comment!

  23. Tina says:

    Thank you for the informative post, Sarah. It helps explain a little more how the confusing world of allergens works. It also explains a bit why my daughter had a high postitive RAST test for wheat, a negative skin test and can eat wheat. It also explains why she had a positive skin test for peanuts but successfully passed a food challenge last week and can now eat peanuts! And why we need to give her peanuts every week to avoid sensitization.

    It’s interesting to read how each family deals with allergens in their home. We do not keep our house allergen-free though we seem to keep less unsafe food in the house than we did previously. My daughter, who is 2-years-old, is allergic to dairy and eggs but we still have milk, yogurt and eggs in the house. We do not have any other small children in the house. Most of the cooking in the house is allergen-free. We of course, are very vigilant about cross-contamination. If we do have something that contains her allergen, I usually try to find a “safe” food that is similar. I just discovered a recipe to make hamburger buns! She has a safe cupboard for her food and knows that she can eat whatever is in there. Since we discovered her allergies, we have never had a reaction at home. So as long as this method works, we will continue to use it. If things change along the way, we will of course revisit our plan.

    • Sarah says:

      Tina, Thank you for reading and for your comment. I think that is always an important thing to be able to do – revisit your plan. It’s good to be able to look at what you’re doing and ask, is this still working for us? If it is, great! If not, time for a new idea. Thank you for sharing how you do things in your home.

  24. AllergEase says:

    What a great article on how we became allergic. This should be a must read for many out there that are unsure of allergies. Thanks again Sarah!

    • Sarah says:

      Thank you very much. 30 Rock was on my tv last night and they made a comment about peanut allergy being “all in head” and I kept wishing I could introduce the show’s writer to my blog, especially the science posts!! We must keep trying to educate.

  25. Barbara says:

    Thank you for this post and your blog. I have only recently discovered it but already you have made me smile, cry and say “ah ha!” Thank you for that.
    In my home I have a 4 yr old with multiple alleriges and an almost 2 yr old who has shown a couple allergies already but is on a very delayed introduction to food – he eats his brother’s allergy-free diet. We are fortunate that neither child has had an anaphylatic reaction or come close – for us it is always a rash/hives. Blood tests come back in the low ranges and he has had cross-contamination issues outside the home that haven’t led to reactions or just mild rashes.
    So, in our home we allow allergens. How we deal with it is a sticker system – red for unsafe foods and green for safe foods. Some foods that are only for the kids (ie jam jar that cannot have cross contamination) have the word ONLY on the green sticker. This system works well in our house – the stickers are a good visual reminder and easy to explain to any guests. For us it works. Again, we are fortunate that our kids seem to have to injest the allergen to react, which I understand is not the case for all children with food allergies.
    Thanks again for your blog!

    • Sarah says:

      Thank you for your sweet words! I am so happy that you found my blog. A sticker system can be a really good way to keep things straight – thank you for sharing what works for you. Have a great week!

  26. Sarah C says:

    I love learning more about the science behind allergies, and you’ve used such a wonderful way of describing the interactions on a cellular level – it’s much easier to understand and therefore, pass along the info to others. I especially find the “false positive” folks interesting, since I’m kind of a backwards version of them – nothing has shown up in prick or blood tests but I still have reactions (and several others in my family have as well, so who knows what it is, but there’s some genetic component there…). I sometimes wonder if I might have “outgrown” some allergies without knowing it since I’ve always turned up negative in testing.

    In any case, thanks a bunch for writing this series in particular, and your blog in general. You really have a great way of writing in a completely normal, yet educational manner.

    • Sarah says:

      Thank you so much for all of your comments. I really do appreciate them and other people do as well. My goal with the science papers is to challenge you but still make it simple enough for you to learn it and teach it to others.
      Have a great weekend!

  27. Ally says:

    This was an excellent and informative post, that we loved reading. The information provided is essential for humans to know, so they can understand allergens, where they come from, and what can be done about them.

Leave a Reply to Sarah Cancel reply

Your email address will not be published.

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>