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 for a few years, starting three months before ragweed season begins in late summer. 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.