Eye Allergy

Eye allergy symptoms can sometimes be confused with infectious conditions.

An eye allergy is an allergic reaction in the eyes. Severe allergic eye symptoms can be very distressing and are a common reason for visits to the allergist, ophthalmologist, and even the emergency room. Occasionally, severe eye allergies cause serious damage that can threaten eyesight.

Approximately 54 million people, about 20% of the U.S. population, have symptoms of allergies. Almost half of these people have allergic eye disease.

People who are more susceptible to allergic eye disease are those with a health history of allergic rhinitis and atopic dermatitis and those with a strong family and/or personal history of allergy. Symptoms and signs usually appear before the age of 30.

Eye allergies mainly involve the conjunctiva, which is the tissue lining (mucus membrane) that covers the white surface of the eyeball and the inner folds of the eyelids. The conjunctiva is a barrier structure that is exposed to the environment and the many different allergens (substances that stimulate an allergic response) that become airborne. It is rich in blood vessels and contains more mast cells (cells that release histamine, a chemical mediator of allergic reactions) than the lungs.

The lacrimal (tear) glands are located in the upper and outer portions of the eye. They are responsible for producing the watery part of tears, which keeps the eye moist and washes away irritants. The tears also contain important parts of the immune defense such as immunoglobulins (antibodies), lymphocytes (specialized white blood cells), and enzymes.

The cornea is the transparent sheath in front of the lens of the eye. The cornea has no blood vessels and very little immune activity.

Allergic conjunctivitis

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.

Conjunctivitis with atopic dermatitis

Commonly called "atopic keratoconjunctivitis," this health 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 the cornea. This form of conjunctivitis usually affects males 3 times more frequently than females and may begin in late adolescence. Its peak incidence is in males aged 30 to 50. It is more common in those who have 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 significant contributing factors 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

Vernal keratoconjunctivitis is an uncommon health 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 and 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 (a type of white blood cell involved in the allergic response), producing so-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.

Giant papillary conjunctivitis (GPC)

This health 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 contact lenses 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.

Contact eye allergies are essentially contact dermatitis of the eyelids. This is an allergic inflammation of the eyelid from direct contact with certain allergens. Women in particular may experience this problem due to allergic reactions to preservatives in eye products and makeup (for example, eye creams, eyeliner or eye pencils, mascara, and nail polish -- from rubbing the eye with the fingers). Other irritants include common over-the-counter (OTC) ointments such as neomycin/bacitracin/polymyxin (Neosporin or Bacitracin) as well as contact lens solutions (especially if they contain thimerosal). Symptoms and signs that are similar to those of a poison ivy rash appear 24 to 48 hours after exposure to the offending agent. The eyelids may develop blisters, itching, and redness. The conjunctiva may also become red and watery. If the eyelids continually come into contact with the offending allergens, the lids may become chronically (long-term) inflamed and thickened.

The best treatment for eyelid allergies is avoidance of the sensitizing agent(s). Changing to hypoallergenic lens solutions, cosmetics, or topical eye care products is usually necessary. The application of mild topical corticosteroid cream for short periods will probably help. As is the case with atopic dermatitis, it is important to treat any secondary bacterial skin infection that may develop.

Eye allergies usually are associated with other allergic conditions, particularly hay fever (allergic rhinitis) and atopic eczema (dermatitis). The causes of eye allergies are similar to those of allergic asthma and hay fever. Medications and cosmetics can play a significant role in causing eye allergies. Reactions to eye irritants and other eye conditions (for example, infections such as pink eye) are often confused with eye allergy. Any kind of irritant, whether environmental, infectious, or manmade, can cause symptoms consistent with eye allergies.

Common triggers for eye allergies can include substances that cause other allergic symptoms, such as pollens, pet dander, mold, dust mites, perfume, cigarette smoke, and diesel exhaust.

The scenario for developing allergy symptoms and signs 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 and discomfort. 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.

Typical symptoms associated with eye allergies include inflammation of the conjunctiva that is caused by a reaction to allergens. The inflammation causes enlargement of the blood vessels in the conjunctiva ("congestion"), resulting in a red or bloodshot appearance of the eyes. These allergy symptoms can range from very mild redness to severe swelling associated with discharge.

The following is a list of health conditions, the symptoms of which are commonly confused with eye allergy.

• Dry eye: This condition results from reduced tear production and is frequently confused with allergy. The main symptoms are usually burning, grittiness, or the sensation of "something in the eye." Dry eye usually occurs in people over 65 years of age and can certainly be worsened by oral antihistamines like diphenhydramine (Benadryl), hydroxyzine (Atarax), Claritin, or Zyrtec, sedatives, and beta-blocker medications.
• Tear-duct obstruction: This is caused by a blockage in the tear passage that extends from the eyes to the nasal cavity. This condition is also typically seen in the elderly. The main complaint is watery eyes that do not itch. Allergy testing will be negative in this case.
• Conjunctivitis due to infection can be caused by either bacteria or viruses: In bacterial infections, the eyes are often "bright red" and the eyelids stick together, especially in the morning. A discolored mucous discharge is often seen in so-called "dirty eyes." Viral conjunctivitis causes slight redness of the eyes and a glassy appearance from tearing. Adenovirus is a major cause of viral conjunctivitis. Herpes viruses, such as the varicella virus that causes chickenpox or shingles, can also affect the eye. Adenovirus infection is very contagious and may be spread by either direct contact, such as hand contact, or in contaminated swimming pools. You should seek medical attention if you suspect any of the above.

The diagnosis of eye allergies can be suspected based on the physical signs and symptoms. An ophthalmologist may perform additional tests to diagnose eye allergies, including an examination of the eyes with a microscope, which can reveal swollen blood vessels on the eye's surface. Another possible test looks for a specific type of white blood cell in the affected eye areas. This involves gently scraping the conjunctiva (the inner lining of the eyelid) and checking for the presence of these cells.

Most people with eye allergies treat themselves and do so quite effectively with OTC eye care products. Most commonly, home care consists of an allergy sufferer flushing the eye with water. With exposure to an allergen in the eye, it is important to thoroughly flush the eye with lukewarm tap water or commercially prepared eyewash solution. If these remedies are not working or if there is eye pain, extreme redness, or heavy discharge, you should seek medical advice. Some conditions, for example, are serious with potential sight-threatening health complications if required treatment is delayed.

Moistening the eyes with artificial tears helps to dilute accumulated allergens and also prevents the allergens from sticking to the conjunctiva. Tear substitutes may also improve the defense function of the natural tear film.

Topical antihistamines and decongestants

Antihistamine eye drops work by blocking histamine receptors in the conjunctiva. The histamine, therefore, is unable to attach to the conjunctiva and exert its effects. They are effective in relieving itching but have little impact on swelling or redness. They have two advantages over antihistamine tablets; there is a quicker onset of action and less drying of the eye. The new generation of topical antihistamines includes emedastine difumarate (Emadine) and levocabastine (Livostin). The side effects of these medications include mild stinging and burning of the eyes upon use, headaches, and sleepiness. However, treatment with antihistamines at the point of irritation is still preferable to treating systemically with oral antihistamines if possible.

Decongestants take the redness away as advertised. However, they do not help relieve itching. They act by shrinking the blood vessels in the conjunctiva. (They are not effective against allergic eyes.) The decongestants oxymetazdine (Visine LR) and tetrahydrozoline hydrochloride (Visine Original) are available OTC. They do have a potential for abuse and should not be used by people with narrow-angle glaucoma, an eye disease characterized by elevated pressure within the eye.

The prolonged use of decongestant nasal sprays can produce a rebound phenomenon in which the medication begins to cause more congestion than it relieves. This phenomenon rarely occurs in the eyes with the repeated use of decongestant drops. The mucous membranes of the eye are different from those of the nose. The eyes can become irritated and less responsive to the drops, but unlike the nose, the eyes tend not to develop "rebound" redness.

A combination of antihistamine-decongestant preparations can provide quick relief that lasts a few hours. They lessen the itch, redness, and swelling and are very useful for milder symptoms. Common combinations include pheniramine with naphcyoline hydrochloride (Naphcon-A or Opcon-A) and antazoline with naphazoline (Vasocon-A). Side effects are minimal, but the drops may become less effective if used for prolonged periods. They do have a potential for abuse and should not be used by people with narrow-angle glaucoma.

Topical mast-cell stabilizers

Mast-cell stabilizers prevent the release of chemical mediators of inflammation from the mast cells. These are effective for all eye allergies. The first of this class of drugs was cromolyn sodium (Crolom or Opticrom), which is available OTC. This topical medicine has been effective for treating mild cases of vernal keratoconjunctivitis and probably mild allergic rhinoconjunctivitis and has no significant side effects. It does have a slow onset of action. The newer agent, lodoxamide (Alomide), is 2,500 times more potent than Crolom and has a faster onset of action. This prescription medicine may be used in children older than 2 years of age and has minimal side effects. One disadvantage is the need to use the drops four times a day, and long-term use is necessary to prevent symptoms.

The most effective mast-cell stabilizer, which also has antihistamine properties, is olopatadine (Patanol). Available by prescription, it is 250 times more effective than Alomide in relieving itching and redness. This drug provides rapid relief of itching and burning eyes. It can also prevent symptoms when used before an exposure or before the pollen season. The drops are very comfortable in the eye and can be used in children as young as 3 years old. The longer duration of action allows dosing twice a day.

Another product, ketotifen (Zaditor), also has dual mast-cell-stabilizing and antihistamine effects. It dramatically reduces itching and redness and gives more rapid relief within minutes.

Topical anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs (NSAIDS) are particularly useful in treating itchy eyes. They reduce redness and swelling to a lesser degree. Ketorolac (Acular) is a topical NSAID, which may cause temporary stinging and burning in 40% of users.

Steroid antiinflammatory eyedrops are very effective in treating eye allergies, but they are reserved for severe symptoms that are unresponsive to other treatments. They must be used with caution in people with bleeding tendencies because they can increase the bleeding risk. Since there are significant risks with long-term treatment, their use should be supervised by an ophthalmologist.

Caution must be taken, however, because of the potential side effects of the long-term use of steroids, even in eye drop form. Side effects of steroids include elevated pressure in the eyes and cataracts. The elevated pressure in the eyes can become glaucoma and lead to damage of the optic (eye) nerve and loss of vision. Cataracts are a clouding or opacification of the clear natural lens within the eye, which can interfere with vision. The purpose of the lens is to focus the light or images that enter the eye. Remember, however, that the side effects of steroids usually occur with long-term use and that steroid eye drops may be very effective when used over the short term. Loteprednol etabonate (Alrex) is a short-acting steroid with fewer side effects that shows great promise in the treatment of allergic eye disease.

Systemic medications

Oral antihistamines, either OTC or prescription (non- or lightly sedating), may be used for itchy eyes. OTC products may cause drowsiness, and both can cause drying of the eyes.

Allergy shots (immunotherapy)

When avoidance of offending allergens and local treatments are not effective, allergy shots may be indicated. Your allergist may suggest this form of treatment when other measures have been unsuccessful.

Here are a few general tips worth remembering:

• Dry eyes may aggravate eye allergy symptoms. Tear substitutes, such as artificial tears, are often forgotten but are an effective lubricant.
• Cold compresses may help, particularly with sudden allergic reactions and swollen eyes.
• Keep eyedrops refrigerated since this makes the application more soothing.

The prognosis is favorable for most patients with eye allergies. Typically symptoms clear up quickly with OTC/home treatment or when the offending allergen is not present anymore. Unfortunately, the symptoms may reoccur depending on the cause of the eye allergy. Health complications are very rare, but medical attention should be sought immediately for any pain or vision loss that occurs or for symptoms that do not resolve within 12 hours.

Complications of eye allergies can include inflammation that is severe enough to temporarily interfere with vision. Scratching or rubbing of itchy eyes can sometimes lead to infections of the eyes or surrounding tissues.

Avoidance is the cornerstone of allergy treatment. It is particularly important to avoid both airborne and contact allergens. Remember, rubbing your eyes is a physical trigger and therefore care should be taken to avoid this.