Get the relief you need with antihistamine and redness reliever eye drops. Opcon-A Antihistamine and Redness Reliever Eye Drops temporarily relieve the itching and redness caused by pollen, ragweed, grass, animal hair, and dander. They are clinically proven eye allergy relief drops that combine an antihistamine for itch relief with a redness reliever that can be used up to 4 times daily. When your eyes are red, itchy, and irritated, get relief with Opcon-A eye drops for allergy relief.