The natural history of peanut allergy in young children and its association with serum peanut-specific IgE.

OBJECTIVES: To observe the nature and frequency of adverse reactions caused by accidental peanut exposure in young children with clinical peanut hypersensitivity and to determine the value of serum peanut-specific IgE levels during follow-up. STUDY DESIGN: Eighty-three children with clinical peanut hypersensitivity diagnosed before their fourth birthdays were contacted yearly to track adverse peanut reactions. Serum peanut-specific IgE levels were determined in 51 of 83 subjects. RESULTS: Fifty-eight percent (31/53) of subjects followed up for 5 years experienced adverse reactions from accidental peanut exposure. Regardless of the nature of their initial reaction, the majority with subsequent reactions (52%, 31/60) experienced potentially life-threatening symptoms. The group with isolated skin symptoms (11/51, 22%) had lower serum peanut-specific IgE levels than the group with respiratory and/or gastrointestinal symptoms (40/51, 78%) (median: 1.25 kU(A)/L vs 11. 65 kU(A)/L, P =.004, Wilcoxon rank sums test). Despite this, there was no threshold level below which only skin symptoms appeared to occur. Four selected subjects had negative double-blind placebo-controlled food challenge responses to peanuts during follow-up. CONCLUSIONS: The majority of children with clinical peanut hypersensitivity followed up for 5 years will have adverse reactions from accidental peanut exposure. Symptoms experienced during subsequent adverse peanut reactions may not be consistent with symptoms reported during initial reactions. Therefore proper education regarding peanut avoidance and treatment of adverse reactions is necessary in all cases of clinical peanut hypersensitivity. Young children who are allergic to peanuts can lose clinical hypersensitivity.

Soy allergy in infants and children with IgE-associated cow's milk allergy.

OBJECTIVES: To determine the prevalence of soy allergy in IgE-associated cow's milk allergy (CMA). STUDY DESIGN: Children <3.5 years with documented IgE-associated CMA (n = 93) were evaluated for soy allergy by double-blind, placebo-controlled food challenge, open challenge, or convincing previous history of an anaphylactic reaction to soy. Children tolerant to soy at entry received soy formula and were followed up for 1 year. RESULTS: Of this IgE-associated CMA cohort (ages 3 to 41 months), 14% (95% CI = 7. 7%-22.7%) were determined to have soy allergy, 12 definitely at entry and 1 possibly after 1 year of soy ingestion. The latter child experienced severe failure to thrive at enrollment and exhibited improved growth while receiving soy during follow-up but was diagnosed with eosinophilic esophagitis at study completion. Improved growth (P <.05) occurred in the non-soy-allergic cohort ingesting soy formula (579 31 mL/d) during the year of follow-up. CONCLUSIONS: Soy allergy occurs in only a small minority of young children with IgE-associated CMA. As such, soy formula may provide a safe and growth-promoting alternative for the majority of children with IgE-associated CMA shown to be soy tolerant at the time of introduction of soy formula.

Patterns of food hypersensitivity during sixteen years of double-blind, placebo-controlled food challenges.

For 16 years the double-blind, placebo-controlled food challenge (DBPCFC) has been used at the National Jewish Center for Immunology and Respiratory Medicine to determine whether adverse reactions to foods do occur in children. The objective of these studies was to explore these reproducible adverse reactions and to characterize them. Although skin testing was performed on all subjects, a history of an adverse reaction to food and to subsequent DBPCFC were the only criteria for entry into this study. Of 480 children studied, 185 (39%) have had positive DBPCFC results. In these 480 children, 245 (24%) of 1014 DBPCFCs showed positive results. Egg, peanut, and cow milk accounted for 73% of the positive DBPCFC reactions, but many foods produced reactions. Skin test results were positive in most children with a positive DBPCFC reaction, but the large number of patients with asymptomatic hypersensitivity limited the accuracy of a positive skin test result alone as a predictor of clinical symptoms during food ingestion. Evaluation of results in this large number of children for a prolonged period revealed reproducible patterns of symptoms, timing, and incriminated foods. Placebo reactions were rare. The procedure was safe. Twelve youngsters with a negative DBPCFC result subsequently had positive reactions to open challenges when large amounts of the challenge food were used. In each of these cases the reactions were limited to areas of direct contact with the food or could be explained by the larger amount of food ingested during the open challenge. Multiple food hypersensitivity has been a rare finding. The DBPCFC should be the "gold standard" for both research and clinical diagnostic evaluations until it is superseded by methods that have yet to be developed.

Natural history of severe reactions to foods in young children.

Nine children with very severe adverse reactions to foods during the first 2 years of life were followed to determine the subsequent course of their reactions. Cautious challenges were given in these children over a period of time. Three of nine children can tolerate the offending food in usual portions; four of nine can tolerate small amounts of the offending food; and two children continue to have reactions to small amounts of the offending food. At some time each of these children have exhibited significant positive wheal and flare reactions when skin tested with extracts of the offending food. This study demonstrates that some children with severe reactions to foods may lose their frightening reactivity to foods over time. Very careful challenges in these patients are thus justified to save families from prolonged anxiety about accidental ingestion, which inevitably occurs.