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Food challenge choices with discrepant allergy testing


A 7 year-old boy with history of eczema since infancy and allergy to milk, egg, soy and peanut with reactions as following: milk caused hives with contact. He passed baked milk challenge. Egg caused localized hives when kissed by his father after he had eaten egg. He passed baked egg challenge. Soy was positive on testing but no known reaction. He had hives during challenge to soy in 2013. He had another challenge to soy in in December 2018 and after 2nd dose, he had hives. He has never ingested peanut.

Specific IgE results as following: In 2013 soy 2.25 and <0.35 in 2018 and 2019. In 2013 egg white 4.15. In 2019 egg white <0.35 and ovomucoid <0.35. In 2013 milk 5.63. In 2019 milk: 0.79 and casein <0.35. In 2013 peanut 8.79. In 2019 peanut <0.35 and peanut component panel all negative.

Skin testing results in 2018 as following: Soy: 7/7, milk: 20/20, egg: 20/20, peanut: 10/10; Histamine: 7/7.

Skin testing results in 2019 as following: Soy, 3/5, milk: 20/30, egg: 15/30, peanut: 5/8; Histamine: 10/20.

Which food challenges would you consider at this time? Since he failed challenge to soy twice despite small reaction on skin testing and negative IgE, how long would you wait before challenging to soy again? Do you think it’s reasonable to challenge to peanut given negative IgE and small reaction on skin testing? Since the skin testing results to milk and egg do not correlate with the IgE testing, what criteria would you use to decide when to challenge to egg and milk?


I asked Dr. David Fleischer for his input regarding your questions. His response is as follows:

"First – I do not know what got hives means here. Patients can get a few hives if the challenge is not carefully done with wiping their hands and mouth (eg patient is fed the food by the nurse – patient does not touch food in any manner; nurse wipes mouth and hands with clean (new) cloth between each dose; and a patient can get a few hives without contact concerns and still make it through the remainder of the challenge (even more concerned these were just contacts reactions with the hives given the history of contact reactions at the time of diagnosis above).

So first question, is how many hives are we talking about here? Where were hives (perioral)? If just a few, I would have considered waiting and seeing if they go away on their own and continued the challenge.

Second – what is this child's total IgE level? If normal <100) and very low (<10), it might explain the low serum IgE levels to foods and larger skin tests to milk and egg.

For soy, again depends on number of hives and where in the challenge the child was deemed to fail. If they made it pretty far in December, then I would consider challenging again, especially with those allergy testing values. Does this child eat other legumes – peas, chickpea, lentil, beans (black, pinto, etc)? If so, it would be unusual to tolerate all of these and not soy.

Would challenge peanut. I – being me and with our setup here at Children’s – would not be afraid to challenge peanut, but that is truly up to the allergist doing it and the family.

I would challenge egg (scrambled) and milk (raw – non baked) now. General guidance for milk and egg IgE levels to challenge are <2 kU/L (same for peanut). Skin tests again are larger, but worth considering given the undetectable IgEs – again is total IgE level really low? If fails raw milk, could consider a baked cheese (pizza challenge).

Again (final again) – at our institution with the food challenge we have set up here, I would feel comfortable challenging all of these. I think it is putting any person responding to this in a difficult position to really comment because I do not know their office setup, experience with doings OFCs, and will not be the one discussing this with the family. Nonetheless, my response is above."

Dr. Fleischer's response points out the many factors that must be considered when deciding on if and when to challenge to a particular food.

I hope this is helpful.

Daniel J. Jackson, MD, FAAAAI