Nasal histamine challenge: a method to predict the efficiency of antihistamine treatment.

Nasal histamine challenge (NHC) was performed on patients suffering from chronic rhinitis. The histamine was administered to the nose in the form of a spray. One hundred sixty-eight patients and 20 healthy subjects were examined. The histamine was sprayed into the nose in seven metered doses, from 0.03 mg to 3 mg. The nose was examined before and 4 minutes after each challenge. A positive reaction to challenge was indicated when the conchae swelled to the point that they impinged against the septum. We found that some patients reacted to a low dose of histamine (0.03 mg to 0.15 mg) while our control group and some other patients reacted positively only to higher doses of histamine (3 mg or more). After the first tests, NHC patients were randomly divided into two groups. One group was treated with placebo and the other group with antihistamines. Three weeks later another NHC was performed (now under treatment) and revealed that patients reacting to low doses of histamine improved significantly with antihistamine treatment, while those reacting to a high dose did not respond to antihistamines. We found the NHC to be a simple test with no complications, and one that is easily tolerated by patients, including children. Nasal histamine challenge helps to identify which patients will improve with antihistamine treatment and aids the evaluation of its efficacy.