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# Keep lawn, vacant lots and easement areas mowed to prevent grasses from blooming and pollinating.

# When mowing grass, wear an aseptic mask to filter out airborne pollen particles and mold spores.

# Following outdoor activity, take a quick shower to rinse pollen off of the skin and out of the hair.

# Keep car windows closed, car A/C on recirculate

# Keep windows at home closed, replace A/C filters

# Stay indoors during peak pollen periods

# Make “non-allergic” landscaping decisions

# Acquire a HEPA-type air filtration system

Pollens (weed, grass, and tree), dust mites, mold spores, animal dander and feathers, and perfumes are among the common allergens causing allergic conjunctivitis. In recent years, topical medications, contact lenses, and contact-lens solutions also have been known contributors to allergic conjunctivitis.

Factors that affect the intensity, frequency, and duration of allergic conjunctivitis include humidity, temperature, and a person’s activity. In general, cooler temperatures seem to alleviate the symptoms of allergic conjunctivitis, whereas hot and dry weather usually intensify and aggravate the condition.

People who complain of severe itching and inflammation should be checked by a doctor for atopic keratoconjunctivitis (a perennial and severe ocular inflammatory condition associated with atopic dermatitis, or eczema, in adults) or vernal conjunctivitis (severe ocular itching that occurs in the spring and usually affects children between the ages of 11 and 13).

Type I hypersensitivity (immediate, IgE-mediated) has been extensively studied in animal models to better understand the immunopathology of allergic conjunctivitis.

Different routes of antigen exposure, including direct sensitization of the conjunctiva, as well as injections of protein antigens into the skin (intradermal) and the vitreous of the eye (intravitreal), resulted in a rise of IgE.

In human studies, specific antigens were applied directly to the conjunctiva. Within minutes, the onset of all symptoms seen in allergic conjunctivitis—redness, itching, swelling, and tearing—were evident. Analysis of tears demonstrated a high concentration of chemicals secreted by white blood cells in defense of the invading antigens.

These chemicals (histamine, leukotrienes, and prostaglandins) are responsible for the inflammatory response typically seen with allergies.

The conjunctiva of the eye is a membrane that lines the inside of the eyelid and extends over the white part of the eye (the sclera). The conjunctiva and eyelid normally function as a natural and immunologic barrier to a vast number of foreign invaders, including bacteria and viruses.

A crucial role in the normal defense against ocular invaders is played by many important cells, including mast cells, plasma cells, lymphocytes, and neutrophils—white blood cells and their derivatives. The mast cell, which is found throughout the eyelid and conjunctiva, is one of the most important players in allergic reactions. Plasma cells are actively involved in making antibodies (immunoglobulins) such as IgE. In allergic individuals, IgE is found in their tears and glands that make tears (lacrimal glands). Both immediate (IgE-mediated) and delayed hypersensitivity (lymphocyte-mediated) immune responses have been shown in experimental models of allergic conjunctivitis.

Although red blood cells (eosinophils) are not normally present in the conjunctiva, they may be found in conjunctival scrapings from people with allergic conjunctivitis. The presence of a single eosinophil (or its granules) usually points to allergic conjunctivitis; however, the frequency of finding eosinophils in conjunctival scrapings may vary with the duration of exposure.