4.10 Itchy eyes

Allergic conjunctivitis is quite common. It can be seasonal or perennial. It is a Type I hypersensitivity, an inflammation of the conjunctiva resulting from an immune response to allergens.

The main symptom of allergic conjunctivitis is severe itch. The eyes also look red and irritated. Very simply, the allergens (from cat dander, house mites, pollens, or chemicals, etc) sensitize the T- and B-cells to produce IgE antibodies. IgE then binds and activates the mast cells. The allergens then further cause the rupture of activated mast cells, thereby releasing histamine and other chemicals.

The itchiness is a response of nerve endings to histamine which also causes vasodilation and blood vessel leakage - hence the redness of the eyes and the formation of conjunctival follicles. So the general principle of treating allergic conjunctivitis is to avoid exposure. Failing that, to use a topical fast-acting antihistamine or a slower-acting mast cell stablizer, or even better, a combination antihistamine-mast cell stablizer. And in severe cases, to treat first with topical anti-inflammatories followed by the anti-allergy drops.

The most commonly prescribed combination eyedrops include Patanol, Zaditor, and Optivar. The newer mast cell stablizers include Alamast and Alocril. Sometimes low concentration soft steroids such as Alrex can also be used on a long-term basis. We, however, favor the combination drugs for their efficacy and safety.