(See also Overview of Conjunctivitis.)
Allergic conjunctivitis is due to a type I hypersensitivity reaction to a specific antigen.
Seasonal allergic conjunctivitis (hay fever conjunctivitis) is caused by airborne mold spores or pollen of trees, grasses, or weeds. It tends to peak during the spring, late summer, or early fall and disappear during the winter months—corresponding to the life cycle of the causative plant.
Perennial allergic conjunctivitis (atopic conjunctivitis, atopic keratoconjunctivitis) is caused by dust mites, animal dander, and other nonseasonal allergens. These allergens, particularly those in the home, tend to cause symptoms year-round.
Vernal keratoconjunctivitis is a more severe type of conjunctivitis most likely allergic in origin. It is most common among males aged 5 to 20 who also have eczema, asthma, or seasonal allergies. Vernal keratoconjunctivitis typically reappears each spring and subsides in the fall and winter. Many children outgrow the condition by early adulthood.
Patients with allergic conjunctivitis report having
Findings characteristically include conjunctival edema and hyperemia and a discharge. The bulbar conjunctiva may appear translucent, bluish, and thickened. Chemosis and a characteristic dermatoblepharitis with hyperemia, edema and lichenification of the medial upper first and then lower eyelid, are common. Chronic itching can lead to chronic eyelid rubbing, periocular hyperpigmentation, and dermatoblepharitis.
In people with seasonal and perennial conjunctivitis, fine papillae on the upper tarsal conjunctiva give it a velvety appearance. In more severe forms, larger tarsal conjunctival papillae, conjunctival scarring, corneal neovascularization, and corneal scarring with variable loss of visual acuity can occur.
Usually, the palpebral conjunctiva of the upper eyelid is involved, but the bulbar conjunctiva is sometimes affected. In the palpebral form, square, hard, flattened, closely packed, pale pink to grayish cobblestone papillae are present in the upper tarsal conjunctiva. The uninvolved bulbar conjunctiva is milky white. In the bulbar (limbal) form, the circumcorneal conjunctiva becomes hypertrophied and grayish. Discharge may be tenacious and mucoid, containing numerous eosinophils.
In 3 to 11% of patients, a corneal ulcer develops, causing pain and increased photophobia. Other corneal changes (eg, central plaques) and white limbal deposits of eosinophils (Horner-Trantas dots) may be seen.
Diagnosis of conjunctivitis and differentiation between bacterial, viral, and noninfectious conjunctivitis (see Table: Differentiating Features in Acute Conjunctivitis) are usually clinical. In allergic conjunctivitis, eosinophils are present in conjunctival scrapings, which may be taken from the lower or upper tarsal conjunctiva; however, such testing is rarely indicated.
Differentiating Features in Acute Conjunctivitis
Avoidance of known allergens and use of cold compresses and tear supplements can reduce symptoms of allergic conjunctivitis; antigen desensitization is occasionally helpful. Topical over-the-counter antihistamines (eg, ketotifen) are useful for mild cases. If these drugs are insufficient, topical prescription antihistamines (eg, olopatadine, bepotastine, azelastine), mast cell stabilizers (eg, nedocromil, cromolyn), or nonsteroidal anti-inflammatory drugs (eg, ketorolac) can be used separately or in combination. Topical corticosteroids (eg, loteprednol, fluorometholone 0.1%, prednisolone acetate 0.12% to 1% drops 3 times a day) can be useful in recalcitrant cases or when quick relief of symptoms is important. Because topical corticosteroids can lead to a flare-up of latent ocular herpes simplex virus infections, possibly leading to corneal ulceration and perforation and, with long-term use, to glaucoma and possibly cataracts, their use should be initiated and monitored by an ophthalmologist. Topical cyclosporine drops may be helpful. Corticosteroid or tacrolimus ointment applied to the skin is very effective in the treatment of eyelid atopic dermatitis. Oral antihistamines (eg, fexofenadine, cetirizine, or hydroxyzine) can be helpful, especially when patients experience other allergic symptoms (eg, rhinorrhea).
Seasonal allergic conjunctivitis is less likely to require multiple drugs or intermittent topical corticosteroids.
Allergic conjunctivitis is usually caused by airborne allergens and can be seasonal or perennial.
Symptoms tend to include itching, eyelid edema, stringy or watery discharge, and sometimes a history of seasonal recurrence.
Diagnosis is usually clinical.
Treatment includes tear supplements and topical drugs (usually antihistamines, vasoconstrictors, nonsteroidal anti-inflammatory drugs, mast cell stabilizers, or a combination).