Oral allergy syndrome typically occurs when food is consumed in what state?

Oral allergy syndrome (OAS) primarily occurs when certain foods are consumed in their raw state due to the cross-reactivity between proteins in these foods and pollen proteins. This phenomenon is particularly prevalent with fruits and vegetables, where individuals with allergies to specific pollen types (such as birch, ragweed, or grass) may experience allergic reactions upon eating raw produce that contains similar protein structures.

In contrast, cooking typically alters the protein structure in foods, often rendering them less allergenic, which is why many individuals can tolerate these same foods when cooked. Frozen or dried forms of food may not induce reactions in the same way as raw foods do, as the processing usually changes or breaks down the proteins that trigger the immune response. Hence, the raw state of food being linked to OAS is a crucial factor in its understanding.