Background: Immediate hypersensitivity to peanuts is a frequent cause of anaphylactic reactions and deaths in children and adults. Currently, preventive treatment consists of avoidance, which is difficult because of the widespread and often disguised use of peanuts in the food industry.
Methods: Twelve patients with immediate hypersensitivity to ingestion of peanuts were recruited. Half were treated with injections of peanut extract: a maintenance level of tolerance was first achieved by a rush protocol, then maintained with weekly injections for at least 1 year. The other six were untreated control subjects. All patients underwent double-blind, placebo-controlled, oral peanut challenges initially, after approximately 6 weeks, and after 1 year.
Results: All treated patients achieved the maintenance dose of 0.5 ml of 1:100 wt/vol peanut extract by the rush injection protocol. All experienced increased tolerance to double-blind, placebo-controlled peanut challenge and decreased sensitivity on titrated skin prick testing with peanut extract, whereas the threshold to oral peanut challenge and cutaneous reactivity to peanut extract were unchanged in the untreated control subjects. Systemic reactions were common in the treated group both during rush immunotherapy and with maintenance injections. Only three patients remained tolerant of the full maintenance dose. The increased tolerance to oral peanut challenge was maintained in the three subjects who received full maintenance doses, but there was partial (n = 2) or complete (n = 1) loss of protection in the patients who required dose reduction because of systemic reactions.
Conclusions: Injections of peanut extract increase the tolerance of patients with peanut allergy to oral ingestion of peanuts. Injections result in repeated systemic reactions in most patients, even during maintenance injections. For clinical application of this method of treatment, a modified peanut extract is needed.