Do lettuce, onion, or pumpkin cross-react with birch pollen in oral allergy syndrome (OAS)?

From the Research

Among the vegetables mentioned, lettuce and pumpkin can cross-react with birch pollen in oral allergy syndrome (OAS), while onions typically do not. Birch pollen-related OAS commonly involves reactions to certain fruits and vegetables due to proteins that are structurally similar to the major birch allergen Bet v 1 1. Letting and pumpkin contain proteins that can cross-react with birch pollen allergens, potentially causing symptoms like itching, tingling, or swelling of the lips, mouth, and throat in sensitive individuals. Onions, however, belong to the Allium family and generally do not contain the proteins that cross-react with birch pollen allergens. Some studies have shown that certain foods can cause cross-reactivity with birch pollen, including apples, peaches, and cherries 2, but the most recent and highest quality study suggests that the major birch allergen Bet v 1 is responsible for the cross-reactivity 1. Individuals with birch pollen allergy who experience oral symptoms after eating raw lettuce or pumpkin should consider cooking these vegetables, as heat often denatures the allergenic proteins, reducing their ability to trigger reactions 3. It's also worth noting that some studies have found that certain proteins in chicory can cross-react with birch pollen, causing oral allergy syndrome 4, but this is not directly relevant to the question of lettuce, onion, and pumpkin. The key takeaway is that lettuce and pumpkin can cross-react with birch pollen in OAS, while onions do not, and that cooking these vegetables can help reduce the risk of an allergic reaction. Some of the key points to consider when evaluating the risk of cross-reactivity include:

• The type of protein present in the food
• The similarity of the protein to the major birch allergen Bet v 1
• The individual's sensitivity to birch pollen and other allergens
• The effect of cooking on the allergenic proteins. Overall, the evidence suggests that lettuce and pumpkin can pose a risk of cross-reactivity with birch pollen in OAS, while onions are generally safe to eat.