The Food and Drug Administration yesterday announced approval of the first antihistamine drug to relieve sneezing and runny noses without causing drowsiness.

"Especially in this season of high pollen counts, this is good news for some of the 40 million Americans with allergies who may fear the typical sedative side effect of antihistamines," said a statement from Health and Human Services Secretary Margaret M. Heckler.

The drug, chemically known as terfenadine, will be available by prescription only.

It will be sold under the trade name Seldane by Merrell Dow Pharmaceuticals Inc. of Cincinnati. It will be available in pharmacies across the nation within a month, to be administered in twice-daily pills at a cost ranging between $1 and $1.40 a day, according to the company.

The FDA noted that Americans spend more than $500 million yearly for relief from seasonal allergic rhinitis.

Inhaling pollen from trees or weeds can trigger an immunological reaction that releases a histamine, which produces such symptoms as runny noses, sneezing, tears and itchy noses and eyes.

Tree pollen is the worst in the spring while weed pollen causes the greatest problems in the late summer or fall.

Antihistamine drugs, first introduced in 1946, block certain receptors to these substances, but FDA said that all previous drugs on the market also have affected the central nervous systems of a significant number of persons who take them, causing some degree of sedation.

FDA Commissioner Dr. Frank E. Young called terfenadine "the first representative of a new class of non-sedating antihistamines."

Company and FDA press releases said that tests on patients in Europe and the United States found the drug to be as effective as traditional antihistamines.

Consumers of the new drug, however, were about as likely to feel sleepy as were users of placebo or inactive drugs, about 9 percent in both groups.

In contrast, 22 to 26 percent of people who took traditional antihistamines reported drowsiness.

Seldane, already sold in more than 20 countries, is the market leader in several of them, including Canada and the United Kingdom, a company spokesman said.