Eighteen patients affected by itching, urticaria, eczema, angioedema, and asthma related to food-stuff intake were studied and classified in two groups (true food allergy and pseudoallergy) on the basis of clinical data, skin prick tests, total and specific IgE levels (PRIST and RAST) and double-blind challenge test. Autologous mixed lymphocyte reaction (AMLR) and T cell activation markers were thought to be tests possibly useful to discriminate between 'true' food allergy and 'pseudoallergy'. The present study failed to show either a significant increase in T cell activation markers (MLR4, Ia) or a significant decrease in AMLR proliferation in such subjects as compared to normal controls. In addition, we found no differences between 'true' allergic and 'pseudoallergic' patients on the basis of the parameters evaluated. Although the AMLR defect was reported both in asthma and in dermatitis, and therefore was thought to be related to atopy, the present data do not confirm this hypothesis in 'true' food allergy.