Oral allergy syndrome (OAS) is primarily caused by cross-reactivity between pollen allergens and similar proteins found in certain raw fruits, vegetables, and nuts. Essentially, if you're allergic to pollen (from trees, grasses, or weeds), your immune system may also react to proteins in these foods that are structurally similar.
Understanding Cross-Reactivity
Here's a breakdown of how cross-reactivity leads to OAS:
- Pollen Allergy: People with pollen allergies are sensitized to specific proteins in the pollen. Their immune system identifies these proteins as threats.
- Similar Proteins in Food: Many raw fruits, vegetables, and nuts contain proteins that closely resemble these pollen allergens.
- Immune System Confusion: When someone with a pollen allergy eats these foods, their immune system mistakenly identifies the food proteins as pollen allergens and triggers an allergic reaction. This reaction is usually localized to the mouth and throat.
Common Triggers
The specific foods that trigger OAS often depend on the type of pollen allergy a person has. Here are some common examples:
- Birch pollen allergy: Frequently associated with reactions to apples, pears, peaches, cherries, plums, almonds, carrots, celery, and soy.
- Ragweed pollen allergy: Often linked to reactions to melons (cantaloupe, watermelon, honeydew), bananas, and zucchini.
- Grass pollen allergy: May cause reactions to peaches, celery, tomatoes, and oranges.
Why Raw Foods?
Cooking can often denature (alter the shape of) the proteins responsible for the allergic reaction, reducing or eliminating the OAS symptoms. This is why many people with OAS can tolerate cooked fruits and vegetables, but react to them when they're raw.
Symptoms and Severity
OAS symptoms are usually mild and localized to the mouth, lips, tongue, and throat. Common symptoms include:
- Itching
- Tingling
- Mild swelling
While rare, more severe reactions like anaphylaxis can occur. If you experience difficulty breathing, wheezing, or throat tightness, seek immediate medical attention.
Diagnosis and Management
Diagnosis usually involves a review of your allergy history and potential allergy testing. Management strategies include:
- Avoiding trigger foods: The most effective way to prevent OAS.
- Cooking fruits and vegetables: Heat can break down the allergenic proteins.
- Peeling fruits and vegetables: Sometimes, the allergenic proteins are concentrated in the skin.
- Antihistamines: Can help relieve mild symptoms.
- Epinephrine auto-injector (EpiPen): Prescribed for those at risk of severe reactions.
