Q. Is it true that patients with immune problems shouldn't take over-the-counter antihistamine?

A. Antihistamines are common medications used to treat allergies such as hay fever. They block the action of histamine, a substance in the body which is released when an allergic person is exposed to certain allergy triggers such as dust or pollen. The histamine causes blood vessels to expand resulting in typical allergy symptoms such as sneezing, itchy eyes, and runny nose. Antihistamines can be purchased without prescription, but some people experience drowsiness as a side effect. The prescription antihistamines are longer acting (12-24 hours) and unlikely to cause drowsiness.

The package insert required by the F.D.A. does not mention anything about a restriction or precaution according to immune status. These drugs can interact with other drugs a person may be taking so there may be circumstances in which antihistamines cannot be taken. Your doctor can advise whether this applies to the situation mentioned.

http://www.nlm.nih.gov/medlineplus/druginfo/antihistaminessystemic202060.html

http://archinte.ama-assn.org/issues/v158n17/ffull/ilt0928-1.html

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