Eyes can become red, swollen, watery, and itchy from an allergic reaction. Severe allergic eye symptoms can be very distressing and could even cause serious damage that can threaten eyesight. It is estimated that approximately 54 million people (about 20% of the U.S. population) have allergies. Almost half of these have allergic eye disease.
Eye allergies usually are associated with other allergic conditions, particularly hay fever (allergic rhinitis) and atopic eczema (dermatitis). Not only this but medications and cosmetics could also play a significant role in causing eye allergies. Reactions to eye irritants and other eye conditions (for example, infections such as pinkeye) are often confused with eye allergy.
The eyes are an easy target for allergies. When you open your eyes, the conjunctiva becomes directly exposed to the environment. The scenario for developing allergy symptoms is much the same for the eyes as that for the nose. Allergens cause the allergy antibody IgE to coat numerous mast cells in the conjunctiva. Upon reexposure to the allergen, the mast cell is prompted to release histamine and other mediators. The result is itching, burning, and runny eyes that become red and irritated due to inflammation, which results in congestion. The eyelids may swell, even to the point of closing altogether. Sometimes, the conjunctiva swells with fluid and protrudes from the surface of the eye, resembling a “hive” on the eye. These reactions may also induce light sensitivity. Typically, both eyes are affected by an allergic reaction. Occasionally, only one eye is involved, particularly when only one eye is rubbed with an allergen, as this causes mast cells to release more histamine.
Allergic conjunctivitis, also called “allergic rhinoconjunctivitis,” is the most common allergic eye disorder. The condition is usually seasonal and is associated with hay fever. The main cause is pollens, although indoor allergens such as dust mites, molds, and dander from household pets such as cats and dogs may affect the eyes year-round. Typical complaints include itching, redness, tearing, burning, watery discharge, and eyelid swelling. To a large degree, the acute (initial) symptoms appear related to histamine release.
The treatments of choice are topical antihistamine drops such as olopatadine (Patanol), decongestants, and the newer mast-cell stabilizer medications. Topical steroids should be used only if prescribed by a doctor for severe reactions and on a short-term basis because of the potential for side effects. In general, oral antihistamines like loratadine (Claritin) or cetirizine (Zyrtec) are the least effective option, but they are often used for treating allergic rhinitis together with allergic conjunctivitis.
Rubbing itchy eyes is a natural response. However, rubbing usually worsens the allergic reaction due to the physical impact on the mast cells, which causes them to release more mediators of the immune response. So do not rub your eyes!
Conjunctivitis with atopic dermatitis
Commonly called “atopic keratoconjunctivitis,” this condition is a notorious cause of severe eye changes, particularly in young adults. Atopic keratoconjunctivitis implies inflammation of both the conjunctiva and cornea. “Kerato” means pertaining to the cornea. This form of conjunctivitis usually affects adolescent boys (three times more frequently than girls) and is more common in those who had atopic dermatitis in early childhood. The condition is characterized by intensely itchy, red areas that appear on the eyelids. A heavy discharge from the eyes can occur, and the skin of the eyelid may show scales and crusts. In severe cases, the eyes become sensitive to light, and the eyelids noticeably thicken. If managed poorly, there can be permanent scarring of the cornea due to chronic rubbing and scratching of the eyes. This scarring can cause visual changes.
The triggers for atopic keratoconjunctivitis appear to be similar to those of atopic dermatitis. A search for common food allergies, such as eggs, peanuts, milk, soy, wheat, or fish is important. Airborne allergens, particularly dust mites and pet dander, have been overlooked as a significant contributing factor and should be evaluated and controlled.
The hallmark of treatment for allergic conjunctivitis is the use of potent antihistamines (similar to those used in atopic dermatitis) to subdue the itching. Topical antihistamines, mast-cell stabilizers, and the short-term use of oral steroids are all beneficial for relief of the itching. Occasionally, an infection of the area (usually with staphylococcus, commonly referred to as “staph”) worsens the symptoms, and antibiotic treatment may help control the itching. Allergy shots are useful in selected cases.
Atopic keratoconjunctivitis can lead to cataract formation in up to 10% of cases. In rare cases, blindness can occur.
Vernal keratoconjunctivitis is an uncommon condition that tends to occur in preadolescent boys (3:1 male to female ratio) and is usually outgrown during the late teens or early adulthood. (Vernal is another term for “spring.”) Vernal keratoconjunctivitis usually appears in the late spring and particularly occurs in rural areas where dry, dusty, windy, and warm conditions prevail. The eyes become intensely itchy, sensitive to light, and the lids feel uncomfortable and droopy. The eyes produce a “stringy” discharge and, when examined, the surface under the upper eyelids appears “cobblestoned.” A closer examination of the eye reveals severe inflammation due to the vast number of mast cells and accumulated eosinophils, producing so-called called “Trantas dots.”
Improper treatment of vernal keratoconjunctivitis can lead to permanent visual impairment. The most effective treatment appears to be a short-term course of low-dose topical steroids. Topical mast-cell stabilizers and topical antihistamines can also be beneficial. Wraparound sunglasses are helpful to protect the eyes against wind and dust.
Keratitis, or the inflammation of the cornea, in vernal and atopic keratoconjunctivitis is largely caused by a substance that is released from the eosinophils, called major basic protein.
Giant papillary conjunctivitis (GPC)
This condition is named for its typical feature, large papillae, or bumps, on the conjunctiva under the upper eyelid. These bumps are likely the result of irritation from a foreign substance, such as contact lenses. Hard, soft, and rigid gas-permeable lenses are all associated with the condition. The reaction is possibly linked to the protein buildup on the contact lens surface. This condition is believed, in part, to be due to an allergic reaction to either the contact lens itself, protein deposits on the contact lens, or the preservative in the solution for the contact lenses. Redness and itching of the eye develop, along with a thick discharge.
Allergy to contact lenses is most common among wearers of hard contact lenses and is least common among those who use disposable lenses, especially the one-day or one-week types. Sleeping with the contact lenses on greatly increases the risk of developing GPC.
The most effective treatment is to stop wearing the contact lenses. Occasionally, changing the type of lens in addition to more frequent cleaning or using disposable daily wear lenses will prevent the condition from recurring.
The giant papillae on the conjunctiva, which are characteristic of GPC, however, may persist for months despite these measures. Eye medications, such as cromolyn (Opticrom) or lodoxamide (Alomide), often are used in this condition, sometimes for several months. Contact lenses should not be worn while these medications are being used.