Sesame is a major allergen in countries where it is a common food. It was noted that an increasing number of members of the UK charity, the anaphylaxis campaign, were reporting allergy to sesame. This study, sought to examine features of sesame allergy among members of the Anaphylaxis Campaign (which supports those at potentially life-threatening risk from allergies) focusing on clinical symptoms and features of the foods implicated. A physician-designed questionnaire was sent by post to 400 members of the Anaphylaxis Campaign who reported avoidance of sesame. Two hundred and eighty replies were received (70%). Twenty-three replies (7%) were excluded and 96 replies (24%) came from subjects who avoided sesame but had never reacted to it. One hundred and fifty people (54%) reported 288 reactions to sesame. 89% of reactive subjects reported other atopic diseases and notably 84% were also nut/peanut allergic. One in six (17%) had suffered potentially life-threatening symptoms, with 65% of severe reactions happening on first known exposure. The age of first reaction ranged from 6 months to 65 yr. The majority of reactions reported (91%) involved foods or dishes which had sesame as a deliberate ingredient, rather than sesame as an accidental contaminant. Respondents represented a well-informed and highly selected group of people at risk from potentially life-threatening allergies. Sesame should be identified clearly as an ingredient and separately from nuts and peanuts when it may be an allergen contaminant. People at potential risk need clear allergy diagnosis and informed guidance to enable them to avoid this key allergen more easily.