WHITEHOUSE STATION, N.J. (AP) — U.S. regulators have again approved a Merck & Co. tablet for gradually reducing seasonal allergies, this time for ragweed pollen.

Ragwitek tablets dissolve quickly under the tongue. Patients are to take one daily, from three months before ragweed season begins until it ends, for a few years. The Food and Drug Administration approved it for patients aged 18 through 65.

Whitehouse Station, N.J.-based Merck’s tablet for spring grass allergies, Grastek, was approved Monday for patients aged 5 to 65.

Both offer an alternative to medicines that just temporarily relieve symptoms or years of uncomfortable allergy shots.

The shots and tablets work by gradually tamping down immune response to allergy-triggering substances and reducing sneezing, runny noses and itchy, watery eyes.

Ragwitek and Grastek should be available in pharmacies by April 30.