- Hourihane J,
- Roberts S,
- Warner J
Purpose of the Study
To determine whether there are any differences between children who remain mildly or moderately allergic to peanut and children with similar histories but a negative reaction on challenge with peanut.
One hundred fifty-five children from Southampton and 75 children from south Manchester referred to the regional pediatric allergy clinic for evaluation of suspected peanut allergy between April 1995 and December 1996.
Children were determined allergic to peanuts with a constellation of typical symptoms 3 years before presentation. Patients were selected for challenges according to the clinical needs in each case. Some were because of negative skin tests despite convincing histories. Those with positive skin tests were challenged because of remoteness of their last reaction or parental request. Those with history of life-threatening reactions were not challenged. Resolvers were children considered no longer allergic if they a) had a clear history of prior reaction to peanut, and b) had a negative formal open challenge. Case controls were matched for age and sex. In addition to skin testing, total serum immunoglobulin E (IgE) was measured using enzyme-linked immunosorbent assay.
A total of 120 subjects were challenged with peanut. Twenty-two cases of resolved peanut allergy were identified but only 15 had suitable positive controls. Allergy to other foods was less common in resolvers (2/15) than persisters (9/15) (P = .02). Skin tests were available for 13/15 resolvers and 14/15 persisters. The two resolvers without skin tests had raised IgE levels of 34 and 280 IU/ml. Eight resolvers had negative skin tests. No persister had negative skin tests. None of the five resolvers with positive prick skin tests had a wheal of >5 mm compared with 17/21 persisters, P < .0001. With cutoff of 6 mm for skin tests, positive predictive value was 100% and negative predictive value was 80%. Total IgE and peanut specific IgE concentrations did not differ between groups. Follow-up for 2 years after challenge showed that 12/14 had not eaten peanuts since challenge. Five of the 12 had eaten them but disliked them. Six ate peanuts without problems, and one resolver vomits after peanuts but still enjoys them despite vomiting. Two persisters who were rechallenged had similar reactions.
Appropriately trained clinicians must be prepared to challenge children with peanut as some will be tolerant despite a history of reactions and positive skin tests. Peanut allergy in a small but significant proportion of young children may resolve much like egg or cow milk allergy. Skin wheal size to peanut predicts reactivity but not severity.
This analysis is the first report of resolution of apparent peanut allergy and offers some hope to patients given this diagnosis early on in life. However, the small final sample size does not allow one to make accurate predictions based on skin tests or IgE levels as far as who will become resolvers. It seems that finding appropriate positive controls was difficult. Furthermore, many of these resolvers may have never had true peanut allergy to begin with. Large populations of these patients must be analyzed to define the true natural history of peanut allergy. However, this is an important study in regards to new awareness of the possibility of resolution of peanut allergy in selected patients.