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.

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.

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.

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. (J Pediatr 2000;137:749-55)