Take extra care when buying foods that are sold loose, such as bread and baked products at delicatessen counters and in-store bakeries. The seeds may not be obvious. They could be hidden in the dough for example, and products can be contaminated with seeds from other products at the counter.
Sesame seeds are difficult to control in food production. They often become ‘electrostatic’, causing them to cling to charged surfaces such as other foods and clothing, which makes it difficult to prevent cross-contamination. If a food product carries a warning such as “may contain sesame”, it’s best to avoid that food.
Heating does not destroy the part of sesame that cause allergies which means they can still cause allergic reactions when they’re cooked.