Eye allergy introduction
The eyes are the windows to the soul because they reflect our state of mind. This certainly can't be true if our eyes are red, swollen, watery, and itchy from an allergic reaction. 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.
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 pinkeye) are often confused with eye allergy.
What is the basic anatomy of the outer eye?
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 (histamine-releasing cells) 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 component of tears, which keeps the eye moist and washes away irritants. The tears also contain important components of the immune defense such as immunoglobulin (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.
Why are the eyes an easy target for allergies?
When you open your eyes, the conjunctiva becomes directly exposed to the environment without the help of a filtering system such as the cilia, the hairs commonly found in the nose.
Allergy fact
Approximately 54 million people, about 20% of the U.S. population, have allergies. Almost half of these people have allergic eye disease.
People who are more susceptible to allergic eye disease are those with a history of allergic rhinitis and atopic dermatitis and those with a strong family and/or personal history of allergy. Symptoms usually appear before the age of 30.
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 is 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.
What are allergic eye conditions?
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.
Allergy assist
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. Translation: 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.
Allergy alert
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 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.
Allergy fact
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.
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.
What are eyelid allergies (also called contact eye allergies)?
Contact eye allergies are essentially contact dermatitis of the eyelids. This is 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, eye pencils, mascara, and nail
The best treatment for eyelid allergies is avoidance of the sensitizing agent(s). Changing to hypoallergenic lens solutions, cosmetics, or topical eye products is usually necessary. Application of a 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 infection that may develop.
What conditions can be confused with eye allergies?
The following is a list of 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, 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. The herpes virus, such as that which 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.
Allergy assist
- If your eye itches and is "milky" red, it is most likely allergy.
- If it burns, it is probably dry eye.
- If it "sticks" in the morning and is bright red, it is usually bacterial or viral conjunctivitis.
How do we care for allergic eyes?
Most people with eye allergies treat themselves and do so quite effectively with OTC products. 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 complications if required treatment is delayed.
Allergy assist
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.
Avoid the triggers
Avoidance is once again 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 must be avoided.
Topical antihistamines & decongestants
Antihistamine eyedrops 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. But treatment with antihistamines at the point of irritation is still preferable than 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 on the conjunctiva. (They are not really 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.
Allergy assist
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.
Combination 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 drug 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 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 by used in children as young as 3 years old. The longer duration of action allows dosing of twice a day.
Another new 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 antiinflammatory drugs
Nonsteroidal antiinflammatory 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 eyedrops may be very effective when used over the short term. Loteprednol etabonate (Alrex) is a new short-acting steroid with fewer side effects that shows great promise in the treatment of allergic eye disease.
Allergy alert
Topical steroids may cause or worsen glaucoma and result in cataracts with long-term use. About 500 drops of a high-dose preparation can cause cataracts. Also, remember that with topical steroid eyedrops, short-term, low-potency preparations are recommended and should only be used under the supervision of an ophthalmologist.
Systemic medications
Oral antihistamines, either OTC or prescription (non- or lightly sedating), may be used for itchy eyes. The OTC products may cause drowsiness, and both can cause drying of the eyes.
Allergy assist
In general, treating topical conditions with topical medications is preferable. Why involve the whole body when locally effective alternatives are available?
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:
- Eyes that are dry may aggravate eye allergy symptoms. Tear substitutes, such as artificial tears, are an often forgotten but are an effective lubricant and a wonderful treatment.
- Cold compresses may help, particularly with sudden allergic reactions and swollen eyes.
- Keep eyedrops refrigerated since this makes application more soothing.
Eye Allergy At A Glance
- Most allergic eye conditions are more irritating than dangerous.
- Allergic or vernal keratoconjunctivitis may result in scarring of the cornea and visual problems.
- Itchy eyes are probably allergic eyes.
- Topical antihistamine/decongestant preparations are effective and safe for mildly itchy, red eyes.
- Patanol, a topical mast-cell stabilizer, is a safe, highly effective, long-acting treatment.
- Topical steroids should be used with caution and under the supervision of an ophthalmologist.
- If in doubt, seek medical advice sooner rather than later.
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