The following video explains eye allergies

Eye allergies, called allergic conjunctivitis, are a common condition that occurs when the eyes react to something that irritates them (called an allergen). The eyes produce a substance called histamine to fight off the allergen. As a result, the eyelids and conjunctiva — the thin, filmy membrane that covers the inside of your eyelids and the white part of your eye (sclera) — become red, swollen and itchy, with tearing and burning. Unlike bacterial or viral conjunctivitis, allergic conjunctivitis is not spread from person to person.

People who suffer from eye allergies usually (though not always) have nasal allergies as well, with an itchy, stuffy nose and sneezing. It is usually a temporary (acute) condition associated with seasonal allergies. However, in other cases, eye allergies can develop from exposure to other environmental triggers, such as pet dander, dust, smoke, perfumes, or even foods. If the exposure is ongoing, the allergies can be more severe, with significant burning and itching and even sensitivity to light.