Allergies to Peanuts | Peanut Component Testing

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Hi, my name is Dr. Chet Tharpe, and I’m a board-certified allergy specialist in South Carolina.Today I am going to discuss a post from the food allergy treatment talk group on Facebook,where a mother reports that her now 19-month-old was diagnosed with having a peanut allergynine months ago when he was 10 months old. The post makes it sound like he had a reaction to aBamba snack which if you are unfamiliar are popular airy, melt in your mouth peanut buttertreats often used for peanut butter introduction at young ages since they don’t pose much risk forchoking. However, she doesn’t describe the reaction specifically.

She posted her child’s peanut component IgE test results on Facebook from the visit when hewas 10 months old and states that COVID has delayed further follow up with the allergist. Shestated she just needed help understanding the bloodwork and wanted input from the group toknow if the numbers were considered high or low.

To briefly summarize the bloodwork, there were six peanut component proteins that were tested:ara h 1, 2, 3, 6, 8, and nine. So, I’ll briefly summarize what these components are: The threemajor peanut component proteins we’re most familiar with are ara H 1, 2 and 3. These are whatwe call seed storage proteins and they’re thought of as the major peanut allergens that can causeanaphylaxis. Ara H 2 is worth discussing briefly as it outperforms whole peanut IgE in predictingclinical peanut allergy.

Ara h 6 is actually very closely related to ara h 2 and we can sort of think of them as the samething for our purposes. Ara h 8 is a minor allergen that closely resembles the birch allergen, Betv 1. And it’s mainly associated with milder symptoms in the mouth and throat area, often calledoral allergy or food pollen syndrome but not anaphylaxis.

Lastly, ara H 9 is a lipid transfer protein that’s predominantly a major allergen in peanut allergicpatients in the Mediterranean. It can also induce a severe reaction or anaphylaxis.

So, why would a physician order component testing? Well, as discussed with ara H 2, these components can help us determine if peanut may in fact have been a culprit allergen when the history is not so clear because it has such a strong ability to predict clinical allergy. Patients with mild or possibly even no symptoms to peanuts, who have detectable ara h 1, 2 or 3 levels, have a higher risk of having an anaphylactic reaction to peanuts. On the other hand, when a patient has minor symptoms to peanut such as mouth irritation and has known tree pollen or specifically birch allergy, a positive ara h 8 test by itself predicts a high likelihood that the patient will tolerate peanut. Thus, the likelihood of having an allergy, putting the history (or lack there of) together with testing, can assist in making a decision if an oral food challenge should be pursued if the risk is low, or put on hold if the risk for reaction is too great at the time.

So those are some of the scenarios where component testing can be helpful. However, for peoplewho have experienced immediate systemic symptoms to peanut such as mouth swelling, rash,vomiting, shortness or breath, or wheeze where there is a positive skin or blood test and just adefinitive slam dunk diagnosis of a peanut allergy, component testing is probably unlikely toprovide additional information that’s going to change the management of the patient and thus isnot necessary.

Ok so back to the post. In this case, this 10-month-old at the time was tested for these peanutcomponent proteins and was only positive for ara h 2, ara h 3, and ara h 6. Remember, ara H 2and 6 are closely related, and just for context, the ara h 2 level was 2.2, the ara h 6 level wasactually 7.3. The ara h 3 level was just .2. Ara h 1, 8 and 9, were all negative. Thus, with the arah 2, 3 and 6 positivity, this patient has a high likelihood of an anaphylactic reaction to peanutwith consumption. Thus, a food challenge would be risky at that point in time and strictavoidance should occur.

The mother asked the group to give her insight as to whether these numbers were consideredhigh or low. As we have discussed in the past with respect to food allergy, it all depends on thehistory of the reaction. Positive IgE numbers themselves do not diagnose food allergy. Positivenumbers denote what we call sensitization. But they do not tell us whether someone is trulyallergic or not. And the high or low value is actually relative. We really want to try to start withsymptoms. And then the positive result is what confirms allergy. However, the positive result byitself and without symptoms, is not diagnostic of allergy and again, is labelled as sensitization orbeing sensitized.

And so high or low numbers in general are actually not relevant and at this point not relevant in this person’s case. I can tell you from personal experience, I have had patients with very high peanut levels that we’ve picked up for various reasons who eat peanuts all the time. I can recall one patient who had a peanut IGE level in the 90s, and she ate peanuts without symptoms whatsoever. On the contrary, I have had patients with negative peanut IgE tests and negative skin tests, but very compelling histories indicating peanut was in fact the culprit allergen. And when I have challenged them, they’ve reacted very strongly confirming their allergy. Obviously, in this case it’s not the identifiable IgE type of reaction that we are used to seeing that’s occurring. It’s some other type of serious immune reaction that’s extremely concerning. And I’ve seen that on a few occasions and thankfully, I can probably only count the number of times that has happened on one hand. However, most needed epinephrine and I’m relieved that we did the challenge in my office as opposed to having the patient do it at home. So that’s where again the history is the most important part, the numbers are supportive, but the history is the most important part.

Going forward with this patient, I would use these components as a baseline and considerredrawing the levels in about a year from when they’re initially checked. If anything you considerthe numbers high or low as compared to a previous year but not based on any level in particularand I would definitely not compare these levels to another patient’s levels as everyone’s historyof reactions and allergy scenarios are unique. Ideally, we’d want to see these numbers goingdown. And if we did see them going down to a minimal level, or maybe even hopefully anundetectable level, and the recent history indicates it would be safe, we would consider a foodchallenge.

So, at this moment in time, it would be continuing to avoid peanut and all peanut containingproducts. This child should have a food allergy anaphylaxis action plan and epinephrine on himeverywhere he went. The parent should be empowered on what to do, should accidental exposureoccur and the child develops symptoms.

So, I hope this has helped you in your respective situation and also hope it will stimulate aproductive discussion with your physician. If you liked this video, please leave me a commentand subscribe to my e-mail list where I can keep you updated on new videos and educationalopportunities through ChetTharpeMD.com. Thanks for your support! Great days are ahead!

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