Allergic conjunctivitis is an eye condition caused by an allergic reaction to substances like pollen, dust mites, or pet dander. It occurs when the immune system overreacts to these allergens, leading to inflammation of the conjunctiva, the thin membrane covering the eye and inner eyelids. Symptoms often include redness, itching, and watery eyes. Treatment typically involves avoiding allergens and using over-the-counter antihistamine eye drops to relieve symptoms. In more severe cases, a doctor may prescribe stronger medications. Maintaining good hygiene and using air filters can also help reduce exposure to allergens.