When life had begun to appear on earth, one of the first things to develop was the eyes. The importance of eyes for the survival of any species on the earth can be gauged from this fact. The defense mechanisms put up by the body to protect eyes are quite striking. It includes the eyelids, eyelashes and the conjunctiva, which covers the eyeball. In spite of all this defense mechanism of the body, eyes continue to be one of the most sensitive organs in the human body and are always open to the attack of airborne allergens. Tears continuously keep the eyes clean but are ineffective when dealing with allergens. An allergy occurs due to the immune response of the body to a foreign particle. Most of the time an allergy is caused by the overreaction of the body. In the eyes, the allergic reaction occurs to the conjunctiva – a transparent membrane covering the eyeball and the under surface of the eyelid. Dust, mold, pet dander and tree pollen are some of the most common allergens. If you are allergic to a particular substance, and when your eyes come into contact with the substance, it will kick start an allergic reaction. It is estimated that more 50 million Americans suffer from various type of allergies. In it, majority of the people suffer from eye allergies. People with allergic rhinitis or atopic dermatitis or strong family history of allergy are more prone to have eye allergies. Causes of Eye Allergies An allergic reaction to the conjunctiva is popularly known as allergic conjunctivitis or �pink eye.’ It varies from soft irritation of the eyes to severe itching, which leads to corneal scaring. Direct contact with the allergen is the main cause of eye allergies. The contact can happen through air, hands and from materials used to rub the eyes. Pollens, spores, pet dander, hair, dust, grass, mold, weeds, certain plants, nail polish, certain medicines and secretions like saliva are some of the most common allergens. The conjunctiva when comes into contact with an allergen produces a chemical called histamine, which causes the symptoms associated with eye allergies. Cigarette smoke, wind, perfumes, air pollution, diesel exhaust also creates irritation to the conjunctiva but this is not included in eye allergies. Symptoms of Eye Allergies Itching is the most important symptom of eye allergy. Redness, watery discharge, swelling of the eyeball, tearing, burning sensation, pain while opening eyelids after sleep, blurred vision, pus formation and the feeling of an alien body in the eye are some of the common symptoms. People wearing contact lens will have discomfort in wearing it. Eye allergies mostly affect both the eyes. Dry eye and tear duct obstruction are sometimes confused as eye allergies. These two types of ailments have similar symptoms to eye allergies. Conjunctivitis can also be caused by bacteria and viruses. Conclusion Eye allergies rarely cause vision impairment. Itching is the most vital symptom of allergic eyes. Although most of the eye allergies are not dangerous, persistent eye allergies should be treated and it is wise to administer drugs after consulting and ophthalmologist.