How to Tell If Conjunctivitis Is Due to Allergy or Infection

Conjunctivitis is one of the most common eye problems across all age groups. It develops when the transparent membrane (conjunctiva) covering the inside of the eyelids and the outer part of the sclera (the white part) of the eyeball becomes inflamed. When small blood vessels in the conjunctiva swell and dilate, they become more visible, causing the eye to turn red. Conjunctivitis can have many different causes, each requiring specific treatment. The most common cause is viral infections, which are highly contagious. However, it may also result from bacterial infection (also contagious) or an allergic reaction. Allergic conjunctivitis is more common in spring due to increased pollen and spores in the air, affecting 15-20% of the population. While the condition can be bothersome, it rarely affects vision. In most cases, it is mild and resolves without specific treatment. However, depending on the cause, medical intervention might be necessary. Distinguishing between viral, bacterial, and allergic conjunctivitis isn’t easy for non-specialists because symptoms like redness, tearing, irritation, itching, and light sensitivity overlap. Nevertheless, some clues can help identify the probable cause. Allergic conjunctivitis usually affects both eyes, while bacterial and viral forms typically start in one. Viral conjunctivitis often follows a cold or other viral illness and produces watery discharge. Conversely, bacterial conjunctivitis causes thick, yellowish-green discharge that glues eyelids shut, especially in the morning. Intense itching is the hallmark symptom of allergic conjunctivitis, often accompanied by eyelid twitching and a history of allergies. Regardless of suspicions, certain symptoms require immediate consultation with an ophthalmologist, such as eye pain, excessive redness, persistent discharge, blurred vision unimproved by cleaning the eye, worsening symptoms after 5-7 days, fever, or signs of severe infection. High-risk patients, including those with weakened immune systems, contact lens users, and individuals who recently injured their eyes, should seek medical attention at the first sign. Treatment varies based on the underlying cause but commonly includes gentle eye cleaning, artificial tears, and warm or cool compresses. Viral conjunctivitis typically resolves without treatment within 1-2 weeks, though antiviral therapy might be needed for specific viruses. Bacterial conjunctivitis may resolve on its own within 7-10 days but often requires antibiotic drops or ointments, especially in severe cases or among high-risk groups like newborns. Avoiding allergens is key for managing allergic conjunctivitis, supplemented by over-the-counter or prescription antihistamines if necessary. Contact lens wearers should avoid using lenses until symptoms subside and replace contaminated products.