The distribution of individual threshold doses eliciting allergic reactions in a population with peanut allergy

Background: Hidden peanut in consumer products can endanger patients with peanut allergy. Individual threshold doses for eliciting allergic reactions need to be elucidated to assess the risks for development of allergic reactions after accidental is ingestion of peanut in a population with peanut allergy. Objective: We sought to determine the distribution of individual threshold doses in a population with peanut allergy and to correlate these thresholds to the severity of peanut-induced symptoms. Methods: Twenty-six adult patients with a convincing history of peanut-related symptoms, a specific IgE level of 0.7 kU/L or greater, or a positive skin prick test response of 2+ or greater to peanut were included. These patients underwent double-blind, placebo-controlled food challenges with increasing doses of peanut. A threshold dose could be established when objective or repetitive subjective reactions occurred after active doses. Results: All patients had subjective oral symptoms (n = 26), prior subjective gastrointestinal symptoms (n = 14), or objective symptoms (n = 5). Reactions started within 30 minutes after ingestion of peanut, but in 2 patients additional symptoms were delayed by 1 to 2 hours. Threshold doses for allergic reactions ranged from a dose as low as 100 mug up to 1 g of peanut protein. Fifty percent of the study population (95% CI, 30%-70%) already had an allergic reaction after ingestion of 3 mg of peanut protein. Patients with severe symptoms had lower threshold doses compared with those of patients with mild symptoms (P = .027). Conclusions: A substantial part of a population with peanut allergy will react to very low amounts of peanut, requiring accurate declaration of peanut content in consumer products. This is even more important because patients with severe reactions react to lower doses than patients with mild symptoms.