In 2007 I saw an 8 month old boy with atopic dermatitis who had RAST testing done by his pediatrician. He was class 2 to cod and wheat, class 3 to milk, class 4 to soy and egg white and class 5 to peanut. His IgE was 647. His first reaction to foods was at 6 months after eating gelato with macadamia nuts and he developed hives and periorbital edema.

His second systemic reaction to food was at age 11 months when he was fed from his mother's plate (rice, catfish, spices, shrimp, coconut milk) and after 2 bites of rice he was crying and developed erythema around his left eye and edema around his left eye and of his lip. He had no respiratory, skin or GI symptoms. He ate tilapia and fish sticks (cod) and had facial, ocular and perioral edema. Catfish RAST was class 3; tilapia was class 2.

He started eating yogurt, cheese, ice cream, eggs without adverse effects. Hazelnut gelato caused perioral erythema. His parents said drinking milk caused nausea and vomiting. They believe that an exposure to peanut caused perioral erythema and swelling but recall no details and are not certain he ate peanut. In April, 2013 (age 6) he ate 1/4 of a large peanut butter cup and had no reaction.

His most recent skin tests show 4+ to cashew (40 x 18 mm) and peanut (35 x 12 mm) and the almond and hazelnut were 6 and 7 mm larger than the negative control. All fish/shellfish were 4+ (all measured too). sIgE are: peanut 45, cashew 4. Because of his own negative challenge I am considering challenging him to peanut in my office. Would you do this and if so could you give me some suggestions about doing it (with raw peanuts, peanut butter?) and how to increase the amount?

Do I recall correctly that if one eats peanuts without a reaction then continues eating a handful of peanuts (or would a tsp of peanut butter be adequate) 3 times a week they will stay desensitized? And, if they do not continue peanut ingestion on a regular basis they could become sensitized (is it 8%) and have a systemic reaction after the next exposure? Is there any data about the time between the successful ingestion of the peanut and introducing the regular ingestion of peanut in the diet? If 3 months have passed between the successful ingestion and the reintroduction could he have become sensitized in that period of time? Thank you very much for your input.


Thank you for your inquiry.

I am referring your question to Dr. David Fleischer, who is a nationally known expert in food allergy, and who regularly performs food challenges in children.

As soon as we hear from Dr. Fleischer, we will forward his response to you.

Thank you again for your inquiry.

Phil Lieberman, M.D.

We received a response from Dr. David Fleischer regarding your inquiry. Thank you again for your inquiry and we hope this response is helpful to you.

Phil Lieberman, M.D.

Response from Dr. David Fleischer:
The patient has multiple food allergies and a peanut IgE level of 45. He ate 1/4 of a large Reese's PNB cup. 2 large Reese's PNB cups contain only 5 gm of protein (Hershey's website), so at most he ate approximately let's say 0.6-7 gm of peanut since one PNB cup is only 2.5 gm of protein - some of that protein is also from dairy. Therefore, the fact is that he likely just did not reach his threshold to react.

I start most of my peanut challenges at 0.5 gm of peanut butter - the exposure this patient had.

I personally would not challenge this patient with such a high IgE level and large skin test, as there is essentially no chance of him passing a FULL challenge of peanut butter (2 tablespoons or 35 grams). I only challenge patients when their IgE level to peanut is less than 2 kU/L.
You could do a fresh skin test to peanut butter to confirm the sensitivity, and you could do peanut component testing in this patient. I would guess that Ara h 1,2, and 3 would come back positive in this subject. I would only challenge this subject if he had negative Ara h 1, 2 and 3 and ONLY positive Ara h 8, which I highly doubt to be the case.

As far as giving this patient small doses of peanut butter daily, I would NOT recommend this. This is then treating the patient with oral immunotherapy, which is not recommended or FDA approved yet. Unless you have a clinical trial to do so, I would not do this. The 8% mentioned is from a study that looked at recurrent peanut allergy: if a patient outgrows their peanut allergy, then if they do not eat it regularly in their diet after passing a food challenge, then they have an 8% chance of it recurring (not 8% chance of a systemic reaction).

I would not state this patient as having a successful ingestion of peanut as he only consumed less than 1 gm of peanut, far below a full food challenge dose to say he is not allergic to peanut. I would say he has been allergic to peanut all along.
David M. Fleischer, M.D.
Associate Professor of Pediatrics
Division of Pediatric Allergy and Immunology National Jewish Health

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