Definition

The conjunctiva protects the eyeball from germs and aids in eye movement. Conjunctivitis is an inflammation of this conjunctival layer. Allergic conjunctivitis results from a rapid hypersensitivity reaction to environmental allergens. While around 40% of the population experiences allergic conjunctivitis, few seek treatment. Though it does not cause blindness, allergic conjunctivitis can significantly reduce the quality of life due to its discomfort. It falls under the broader category of conditions marked by conjunctival redness and swelling.

Allergic conjunctivitis is the most prevalent form of conjunctivitis. According to the National Health and Nutrition Examination Survey, 6.4% and 29% of 20,010 participants reported eye and nasal symptoms, respectively. Around 40% experienced at least one eye symptom within 12 months. Atopic keratoconjunctivitis, a type of allergic conjunctivitis, typically manifests during adolescence and the fifth decade of life. It can recur independently of the seasons and is often accompanied by atopic dermatitis.

Causes

There are several forms of allergic conjunctivitis:

• Simple allergic conjunctivitis: caused by allergens on the eye surface, typically affecting individuals under 20, with symptoms improving with age.
• Vernal keratoconjunctivitis: likely due to a combination of climate and allergens, more common in males living in dry, warm climates, and often associated with other allergy symptoms like asthma.
• Atopic keratoconjunctivitis: triggered by allergen exposure, atopic dermatitis, and/or genetic predisposition.
• Giant papillary conjunctivitis: caused by allergens and foreign objects touching the eye, such as contact lenses, prostheses, or stitches.

Allergens that can trigger allergic conjunctivitis include:

• House dust
• Insects
• Pollen
• Contact lenses
• Pets
• Fungus
• Temperature, seasonal, and climate changes
• Eye drops (e.g., neomycin, atropine)
• Eyelid cosmetics
• Food allergens

Risk Factors

Risk factors for allergic conjunctivitis include:

• Being a child (30–40%) or young adult
• Exposure to allergens
• Using contact lenses
• Having other atopic conditions, such as asthma or allergic rhinitis
• Family history of allergic conjunctivitis

Symptoms

Symptoms of allergic conjunctivitis include:

• Redness in both eyes
• Itchy eyes
• Swelling of the eyelids
• Burning sensation in the eyes
• Watery eyes
• Foreign body or gritty sensation in the eyes
• Sneezing, itchy nose, and coughing

Diagnosis

To diagnose allergic conjunctivitis, a doctor will inquire about your allergy history, asthma, allergic rhinitis (morning sneezing), and family history of allergies. During a physical examination, the doctor will inspect the conjunctiva. Further examinations may include:

• Allergy skin test: A procedure in which several substances that are known to be allergens will be exposed to patients to observe the body's reaction.
• Blood test: To detect specific proteins or antibodies to allergens like house dust or mold.
• Conjunctival scraping: collecting a small conjunctiva tissue sample to examine red blood cells, noting an increase in eosinophils after allergen exposure in allergic conjunctivitis.

Management

Medical Treatments

To alleviate allergy symptoms, your doctor might prescribe the following medications:

• Antihistamine drops: effective in reducing symptoms but should not be used for more than six weeks without medical supervision.
• Antihistamine drops and vasoconstrictors: Reduce itching and redness. Should not be used for more than 14 days due to the rebound effect, where red eyes may return after stopping use.
• Mast cell stabilizers: Take 3–7 days to reduce the excessive response of mast cells involved in the allergy process.
• Steroid drops: Quickly reduce inflammation symptoms but should not be used without a doctor's supervision as they can cause cataracts and glaucoma.

Home Remedies

Managing allergic conjunctivitis at home involves prevention and symptom relief. Key preventive measures include identifying and reducing exposure to allergens. For symptom relief, applying cold compresses to the eyes for 10-15 minutes daily and using artificial tears can provide comfort.

Complications

Allergic conjunctivitis typically resolves on its own without serious complications. However, it can easily recur and affect quality of life. Recurrent allergic conjunctivitis can lead to prolonged conjunctival inflammation, potentially impairing vision. Long-term use of treatments can cause cataracts. Possible complications include severe eye damage and secondary bacterial infections.

Prevention

Allergic conjunctivitis is not contagious but is triggered by allergen exposure. Do this to prevent recurrence:

• Avoid touching or rubbing your eyes
• Wash hands with soap after and before touching your eyes
• Regularly clean your room, bed linens, and carpets to minimize house dust allergens
• Limit pets indoors if allergic
• Wear glasses to prevent pollen from entering your eyes
• Keep windows closed to avoid pollen, smoke, and pollutants
• Use air conditioning with special filters
• Minimize exposure to strong detergents

When to See a Doctor?

Seek medical attention if you experience eye redness with severe pain, fever, chills, blisters around the eyes, persistent blurred vision, thick white or greenish discharge, or if you see these symptoms occur in a baby under 24 hours old, or if symptoms do not improve within one week or 24 hours after using antibiotics. Immediate medical attention is also necessary if you have conditions like HIV infection, are undergoing cancer treatment, or have diabetes.

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