The conjunctiva is the clear, thin layer that covers the white of your eye and the inside of your eyelids. Conjunctivitis is inflammation (swelling and irritation) of your conjunctiva.
What is allergic conjunctivitis?
Allergic conjunctivitis is a reaction in your conjunctiva caused by something you're allergic to, such as pollen, mold, or dust. Your eye gets swollen, red, and itchy.
Allergic conjunctivitis can be caused by:
-
Seasonal allergies Seasonal Allergy An allergy is when your body's immune system reacts to something harmless, such as food, plants, or medicine. Seasonal allergies are allergies that happen only during the time of year when a... read more to things like mold, tree, weed, or grass pollen (you usually have symptoms in the spring or fall)
-
Year-round allergies Year-Round Allergies Year-round (perennial) allergies result from indoor exposure to airborne substances (such as house dust) that are present throughout the year. The nose is congested, itchy, and sometimes runny... read more to things like dust, animal dander, or feathers (you have symptoms year-round)
There are other causes of conjunctivitis. For example, infectious conjunctivitis Infectious Conjunctivitis The conjunctiva is the clear, thin tissue that lines the inside of your eyelid and covers the white of your eye. Conjunctivitis is inflammation (swelling and irritation) of your conjunctiva... read more 
is caused by a viral or bacterial infection. Also, a speck of dirt, contact lens, or makeup can irritate the conjunctiva and cause conjunctivitis without there being an allergic reaction or infection.
