SummaryBackground Allergy to sesame seeds is often associated with particularly severe reactions, with a high risk of anaphylaxis. The increase in reports of allergic reactions to sesame is probably due to the growing use of sesame seeds or sesame oil in food.Objective To determine the molecular weights of the proteins in three variety of sesame seeds and to study the isoelectric points and the allergenicity of white sesame proteins.Methods Extracts of white, brown and black sesame seeds were prepared. The white sesame extract, mostly used in bakery, was run on SDS‐PAGE and two dimensional electrophoresis. Six sera from patients sensitized or symptomatic to sesame seed were used for Western blotting.Results The protein patterns of the white, brown and black sesame extracts showed major quantitative differences. The white extract had the higher protein concentration and contained 15 proteins of 12–79 kDa, some of them having several acidic isoelectric points. The lowest isoelectric point was 4.9 and the highest was 6.4, giving 35 isoforms. Ten of the 15 proteins (12–57.5 kDa) were recognized by specific IgE. The 12–13 kDa and 22–33 kDa proteins could correspond to the main allergens.Conclusion White sesame seeds contain at least 10 allergenic proteins with acidic isoelectric points. In accordance with previous results, two of them seem to contain the major allergens.