Q: Our 11-year-old has oral allergy syndrome (OAS) that relates to his birch pollen allergy. He gets an itchy and swollen mouth if he eats raw apples, cherries, carrots or peas. Then the other day he ate a few peanuts and got mouth symptoms to those, too! How are my wife and I to know if peanut is now another OAS trigger – or if this is a more serious allergy? Should he carry an auto-injector?
Dr. Sicherer: As you describe, some people with birch pollen allergy experience mouth symptoms with specific raw fruits and vegetables. This is because those foods contain proteins that are very similar to the protein in the pollen. Usually, the symptoms are mild and localized to the mouth.
Cooking the fruits and vegetables breaks down the protein – so foods such as apple sauce, canned cherries, and heated soft carrots may be tolerated without symptoms.
Peanut as well has this birch-related protein. In the form of peanut butter or roasted peanut, it is presumably heated well enough to also substantially inactivate this protein.
In a study of a group of children who were shown through blood testing to only be sensitive to the birch pollen-related protein in peanut, about one in four experienced some mouth itching at the start of a feeding test to peanut. But this symptom resolved, even though the children continued to eat the full serving of peanut.
However, one cannot just assume that mouth itch to a few peanuts is innocent; a new peanut allergy can arise.
To decipher the situation for your child, you will need to work with your allergist who will obtain a more detailed history:
• Blood testing for allergy to the different proteins (or components) in peanut will likely be done to assess whether your son has sensitivity to proteins other than the pollen-related one.
• A feeding test may be needed to confirm that he can tolerate a full serving of peanut.
Allergists tend to decide upon prescribing an auto-injector for pollen-related food allergy based on the specific symptoms and circumstances, but mild allergy to a food like peanut usually does warrant a prescription.
Dr. Scott Sicherer is a practicing allergist, clinical researcher and professor of pediatrics. He is Director of the Jaffe Food Allergy Institute and Chief of Pediatric Allergy and Immunology at the Icahn School of Medicine at Mount Sinai in New York. He’s also the author of Food Allergies: A Complete Guide for Eating When Your Life Depends On It.Submit a Question View all posts by this medical expert.