Nineteen adult patients representing a total of 24 medical histories of immediate adverse reactions to egg or cows' milk underwent 1) standardized questioning about signs/symptoms occurring less than 2 h after ingestion of egg or milk, 2) skin prick test, RAST and histamine release test, and 3) titrated, oral, double-blind, placebo-controlled challenge (DBPCFC) with fresh egg or milk. Eleven medical histories (46%) were confirmed by DBPCFC in 10 patients (53%). All DBPCFC-positive patients experienced gastrointestinal symptoms, and in 80% of the patients, gastrointestinal symptoms were accompanied by respiratory or skin symptoms. Threshold doses varied between 50 mg and 250 g, with 4 patients presenting objective signs following 5 g or less. DBPCFC-positive patients reported significantly more symptoms and had a significantly higher number of positive tests than had DBPCFC-negative patients. None of the tests were in significant concordance with DBPCFC, although RAST showed a sensitivity of 100%. Thus, DBPCFC cannot be substituted in the diagnosis of milk and egg allergy in adults. The use of titrated, fresh foods in DBPCFC proved to be a safe and well-controlled procedure.