Oral allergy syndrome (OAS) is an allergic reaction in which eating certain raw fruits, vegetables, or nuts causes itching, tingling, or mild swelling of the mouth, lips, and throat. It arises from cross-reactivity: the immune system mistakes food proteins for similar proteins in pollens, so birch-pollen sufferers react to apples, carrots, and hazelnuts, while ragweed allergy links to melon and banana. Symptoms are usually mild and brief because the culprit proteins break down quickly and are destroyed by cooking, which is why sufferers often tolerate cooked or canned versions. Severe reactions are uncommon but possible, particularly with nuts. Management involves identifying the pollen-food links, peeling fruit where it helps, and carrying antihistamines; dietitians help patients maintain fruit and vegetable intake by finding safe alternatives rather than abandoning the food groups.