Allergic conjunctivitis occurs when the surface of the eye is exposed to irritants (called antigens) that begin a cascade of reactions leading to inflammation of the ocular surface. Cells on the surface of the eye called mast cells and eosinophils that are pre-sensitized to these antigens release a chemical called histamine which lead to inflammation, vessel dilation, itching, and swelling. It is usually seasonal and worse in the spring to fall when pollen (from trees, grass and ragweed) and spores are in the air, but can occur anytime when associated with common environmental antigens such as pet dander, dust, smoke, perfume, makeup and even food. Many prescription and over-the-counter eye drops including artificial tears contain preservatives that often cause an allergic reaction as well. The symptoms of allergic conjunctivitis include itching, redness in the white part of the eye and/or inner portion of the eyelids, swelling of the eyelids, burning, blurry vision and light sensitivity. The symptoms are usually affect both eyes although it may be worse in one eye. It may also be associated with nasal allergy with symptoms that may include itching of the nose and throat, sore throat, coughing, sneezing, runny nose, nasal congestion, and headache.
Treatment starts with avoiding the primary antigen if it can be identified. Pollen, mold spores, dust, pet danders are common culprits. Monitor the pollen count and stay indoors as much as possible on days when the count is high. Use an air conditioner that filters out pollen and spores, vacuum with a HEPA filter, avoid drying clothes outdoors, change bed sheets and pillow covers often, and shower and change clothes before bed (especially after being outdoors).
Cool compresses can help with the swelling and artificial tears that has been cooled inside a refrigerator can provide symptomatic relief from burning. Artificial tears will also wash out any potential antigens and inflammatory mediators (remember to use preservative free artificial tears as explained above). Prescription anti-histamine drops are very effective and can even help with some of the nasal symptoms as the drop makes its way into the nasal passages through the tear ducts. Many of the modern anti-histamine drops we prescribe only needs to be used 1-2x/day and also prevent the mast cells from releasing histamines to mitigate future allergic reactions. A mild corticosteroid drop is often useful as well especially when there is a lot of inflammation. Oral anti-histamines like Claritin, Allegra, and Zyrtec help with the nasal symptoms but do not significantly improve the symptoms of ocular allergy. They are actually drying to the eye so it should only be used in moderation to treat the non-ocular symptoms. It is also possible to perform a blood or skin prick test to determine what specific antigens you are sensitive to. Once identified, immunotherapy can then be performed by introducing small doses of the antigen by injection or under the tongue so the body can develop a tolerance to the antigen. If you think you may have allergic conjunctivitis or have a history of seasonal allergic conjunctivitis, make an appointment to see one of our board certified ophthalmologists at North Shore Eye/SightMD and be prepared for allergy season!