Timing of onset of allergic symptoms as a response to a double-blind, placebo-controlled food challenge in patients with food allergy combined with a radioallergosorbent test and the evaluation of proliferative lymphocyte responses.

The timing of onset of allergic symptoms in a double-blind, placebo-controlled food challenge (DBPCFC) was combined with a radioallergosorbent test (RAST) and evaluation of proliferative responses of peripheral blood mononuclear cells (PBMCs) in 27 atopic dermatitis patients with hen's egg allergy. Of the 27 patients, 11 showed reactions within 2 h (immediate group), and 16 showed reactions after more than 2 h (nonimmediate group) after ingestion of hen's egg. The RAST scores for hen's egg in the immediate group were significantly (p < 0.01) higher than those in the nonimmediate group, while the proliferative responses of PBMCs to ovalbumin in the nonimmediate group were significantly (p < 0.01) higher than those in the immediate group. These results suggest that the RAST values are related to immediate allergic symptoms in DBPCFC and the proliferative responses of PBMCs are related to nonimmediate allergic symptoms in DBPCFC. The timing of onset of allergic symptoms in DBPCFC will render DBPCFC more useful in the diagnosis of food allergy, including the late-onset reactions to foods.