Health Talk: Oral allergy syndrome

On his first visit to the Carnegie Mellon Café, electrical and computer engineering master’s student Isaac Jones got an unexpected surprise. His chocolate shake hid a toxin-laden garnish in the form of a rolled wafer cookie — Jones is allergic to the hazelnut contained in the cookie’s filling. Nuts are common irritants for those who suffer oral allergy syndrome — a fancy name for allergies that originate from the mouth, or food allergies. Along with nuts, many fruits and vegetables also set off allergic reactions in sensitive individuals.

For Jones, the list includes not only a variety of tree nuts (not peanuts or pine nuts — they are not technically nuts, as the former is a bean and the latter a seed) but also some vegetables like carrots and celery.

When Jones eats an estimated four or five baby carrots, he begins to experience what he describes as a tingling in his mouth and uncomfortable restriction in his throat. Allergy symptoms are caused by mistakes in the immune system. According to Discovery Health’s website, the body produces antibodies to anything it perceives as a foreign invader. In the case of allergens, the immune system incorrectly identifies certain chemicals as toxic. This is what creates the allergic response.
In vegetables, the body is reacting to specific proteins in the cell walls. These proteins are important in the structure of the cell wall. One such protein, called an extensin, ties together the outer and inner layers of the cell wall. Similarly, Jones’ allergy to tree nuts is also set off by a protein. However, there is no evidence that the two allergies are related. Jones explained that while he experiences very similar symptoms when he eats nuts, he also begins to salivate uncontrollably. When Jones was a sophomore in high school, he had his first encounter with nut allergy. At a Super Bowl party, he was eating from a bowl of mixed nuts — mostly cashews and hazelnuts — when he found his mouth was tingling. His mother, an emergency room doctor, advised him to avoid nuts in the future.

Later on, Jones began to feel a similar reaction when eating carrots. While he did not commonly eat many nuts as a child, he said, “it was reasonably common to have a package of raw carrots in lunches. They were very often an after-school snack.”
While it is more common for allergies to be lost during puberty, an article by the Canadian Society of Allergy and Clinical Immunology explained that the chemical changes the body undergoes during puberty may cause allergies to either worsen or even develop during adolescence.

Allergies that develop in later life are most commonly airborne allergies, however. Allergist Clifford Bassett, M.D., explained that many times, oral allergy syndrome is connected to seasonal airborne allergies — one out of every three people who suffer seasonal allergies may experience oral allergy symptoms.

Specific kinds of pollen that set off seasonal allergies relate to foods that are genetically similar. For example, people who find their nose running when they encounter ragweed pollen are more likely to be allergic to bananas or melons. In the case of Jones’ allergy, carrots and celery are related — both are part of the parsley family, including not only parsley, but also dill, anise, cumin, coriander, and mugwort. However, Jones said, “I’ve never knowingly consumed raw mugwort or dill in quantities that would be large enough to trigger a reaction.”

One important element of that statement is the word “raw”: in those who suffer oral allergy syndrome, the food irritant is no longer effective when the food has been cooked. The website of the Children’s Hospital of Philadelphia explains why: “The cooking process changes the protein enough that the immune system does not recognize [the allergen] anymore.” Like anyone with allergies, Jones must pay close attention to what he eats to ensure he does not react negatively to the food. Though he can no longer eat “ants on a log” — a raw celery stick with peanut butter and raisins he used to enjoy as a child — he is aware of his limitations. Now he knows not to eat the wafer cookie in his next Carnegie Mellon Café milkshake; he can give it to his friend instead.