If you have seasonal allergies like hay fever, you are probably familiar with the itching and redness of eye allergies. An allergy is a reaction by the immune system to particles of something the body perceives as harmful. These particles, known as an allergen, trigger the immune system to release large quantities of chemicals to fight off the invasion.
One of the most common of these chemicals is histamine. When excessive amounts of histamine are present, we have common allergic symptoms including red, swollen, sore, and itchy eyes. The most common symptom of eye allergy is itching. Redness or swelling without itching is more likely caused by something other than an allergy.
Types of Eye Allergies
There are several different types of eye allergies. Seasonal allergy in the eyes, also known as seasonal allergic conjunctivitis (SAC), is the most common type. Conjunctivitis is swelling or infection in the membrane that lines the eyelids and outer surface of the eye. In SAC, this irritation is typically caused by airborne pollens during specific growing seasons. Allergic conjunctivitis can also be perennial or year-round. Common allergens for this condition include pet dander and dust.
Eye allergies can also be caused by medications:
• Sudden onset - Topical penicillin, bacitracin, sulfacetamide, and anesthetics are some medications that can cause very sudden symptoms including swelling of the lining of the eyes and severe itching.
• Toxic papillary reactions – Some chemicals including certain antibiotics and antiviral drops and some preservatives can cause a reaction in the tiny blood vessels in the eye that can make the white part of the eye appear red. This reaction typically occurs after taking the medication for a week or more.
• Contact reaction – Chemicals that are applied directly to the skin or eye can cause a gradual build-up of irritation. These can include topical medications as well as cosmetics.
Contact lenses can also cause an allergic reaction, either to the lens itself or to proteins that are present in the tear film between the lens and the eye.