Column: OAS could be a sign of underlying pollen allergy
EDITOR'S NOTE: This is the second part of a series.
Q: How is OAS diagnosed?
A: OAS is diagnosed by obtaining good history from the patient, by looking for physical findings on examination that are consistent with allergic rhinitis, asthma or eczema and by doing allergy skin or blood tests for pollens and foods. In general, patients with OAS are highly allergic to pollens by allergy skin tests or blood tests. Tests for suspected foods may or may not be positive because of the fragile nature of these food allergens (lack of stability and deterioration in quality with time). To overcome this problem, some allergists do what is known as prick-prick test. In this procedure, the suspected fresh fruit or vegetable is pricked with a sterile needle and the same needle is used to prick the skin of the patient. A positive test indicates allergy to the food in question. Even with this procedure results may vary.
Q: How is OAS treated?
A: Until recently, not much could be done about problems faced by patients with OAS. Avoiding the food(s) in question was the only available treatment option. Some patients have found that cooked vegetables and fruits (bananas for example) are tolerated without much problem. In patients who develop systemic symptoms of anaphylaxis, obviously this option is dangerous and should not be followed. Such patients should strictly avoid the offending foods in question and carry self-injectable epinephrine with them at all times for emergency use. A study that was done in Europe few years ago found that majority of patients who had OAS from eating apples and who had underlying allergy to birch tree pollens could eat apples again after undergoing allergy desensitization injections for birch tree pollens for a year. While this finding may not be applicable to other pollens and fruits/ vegetables, nevertheless this study points out that allergy desensitization injections for pollens may play a beneficial role in this condition.
Q: Are there other conditions similar to OAS?
A: Yes. For example, patients who are highly allergic to latex may cross-react with certain tropical fruits such as kiwi, bananas, papaya, avocados, chestnut etc.. Similarly patients who are highly allergic to dust mites may react with shrimp, patients who are highly allergic to cats may cross-react with pork and patients who are highly allergic to feathers may cross-react with eggs. As we understand more about molecular structures of different allergens in pollens, fruits and vegetables, we will be in a better position to solve many of the problems faced by OAS patients.
Natarajan Asokan, M.D., F.A.A.P. is a board certified allergist and immunologist and a board certified pediatrician with more than 25 years of experience as a physician and 8 years of experience as a practicing allergist and immunologist. He treats adults and children with various allergy and immunology problems. He can be reached at 1739, Beverly Ave, Suite 118, Kingman, AZ 86409, Tel: 928-681-5800, Fax: 928-681-5801, or www.trinityallergy.com.