Enzymatic hydrolysis and further processing are commonly used to produce hypoallergenic dietary products derived from different protein sources, such as cow's milk. Lentils and chickpeas seem to be an important cause of IgE-mediated hypersensitivity in the Mediterranean area and India. Some studies have investigated the effects of enzymatic treatments on the in vitro immunological reactivity of members of the Leguminosae family, such as soybean, chickpea, lentil, and lupine. Nevertheless, there are only a few studies carried out to evaluate the effect on IgE reactivity of these food-hydrolysis products with sera from patients with well-documented allergy to these foods. In this study, lentil protein extract was hydrolyzed by sequential action of an endoprotease (Alcalase) and an exoprotease (Flavourzyme). Immunoreactivity to raw and hydrolyzed lentil extract was evaluated by means of IgE immunoblotting and ELISA using sera from five patients with clinical allergy to lentil. The results indicated that sequential hydrolysis of lentil results in an important proteolytic destruction of IgE-binding epitopes shown by in vitro experiments. However, some allergenic proteins were still detected by sera from four out of five patients in the last step of sequential hydrolyzation.