Pollen-food allergy on increase
Having a severe pollen allergy is a headache in itself, but for a growing number of adults, their discomfort is compounded by an associated food allergy condition often described as oral allergy syndrome.
Dr Vincent St Aubyn Crump says oral allergy syndrome was increasing worldwide, and affects about 40 per cent of people with pollen allergy.
“In New Zealand we are seeing a lot of fruit allergy related to silver birch pollen allergy, and this seems to be more of a problem with introduced species. Pollen-food allergy, however, is not only associated with silver birch, but all pollens, which is why I call it pollen-food allergy syndrome,” he says.
In North America, ragweed is the biggest cause of cross-reactions. Mugwort is another plant that we are starting to see more pollen problems with in New Zealand.
There are several risk factors for acquiring pollen-food allergy, and these include:
• having a severe pollen allergy to birch (24 per cent of sufferers are at risk)
• grass (4 per cent of sufferers are at risk)
• birch and grass (35 per cent are at risk)
• and having a latex allergy
“Patients don’t go to their doctor complaining about oral allergy syndrome, because they just avoid the culprit foods. They are usually diagnosed with the syndrome when the come to my practice because of their hay fever, so oral allergy syndrome’s true prevalence is probably underestimated,” he says.
PromiscuousNormally IgE antibodies to a particular allergen are very specific, Dr Crump explains. In a cross reaction, an antibody that is specific for one allergen has the ability to react with a second allergen because the two allergens have a closely related protein.
“It’s just like having a pair of gloves that can fit two different people with similarly sized and shaped hands. This is the case in birch pollen. I think of it as being very promiscuous, as it binds to several closely related foods,” he says.
Pollen-food allergy often begins in adulthood with symptoms of tingling in the mouth and itching, and rarely progresses to anaphylaxis. It usually occurs when fresh fruits and vegetables are eaten, with no reaction when the foods are cooked.
“But we need to be very careful how we diagnose oral allergy syndrome,” Dr Crump cautions, “because it starts with itching in the mouth, which can also occur in peanut and seafood allergy sufferers at the onset of severe anaphylaxis.”
DiagnosisTo diagnose pollen-food allergy, Dr Crump carries out a ‘prick prick’ test.
“I get my patients to bring in a bag of fruit. I prick the fruit and then I prick them with the same instrument. If you rely on the fruit extract supplied by the laboratories, it’s a waste of time because the extract has degraded significantly by the time you use it.”
The treatment for pollen-food allergy is simply avoidance, although immunotherapy to pollens has been shown to decrease the symptoms. Studies have found that almost 40 per cent of patients who have had immunotherapy treatment have a significant reduction of their oral allergy syndrome symptoms and over 22 per cent become completely symptom free.
“New Zealand native plants are a lot less allergenic than introduced plants,” Dr Crump points out. “It’s the introduced plants that cause problems. With olive trees becoming very popular, I’m wondering if we can expect an epidemic of olive- and mugwort-related food allergy in the future?”
Foods associated with birch pollen allergy
Article has been reprinted from Allergy Today Spring Issue 122. For an annual subscription, click here.