What should you know about half eye red?

A red patch can occur when small surface blood vessels widen or leak. Dryness, dust, rubbing, a minor surface injury, contact lenses, or irritation may affect one area. Itching and watery discharge can fit [Allergic Conjunctivitis](/conditions/allergic-conjunctivitis/), while sticky discharge and redness may occur with [Conjunctivitis](/conditions/conjunctivitis/). The appearance alone cannot identify the cause.

Pain, blurred vision, strong light sensitivity, a severe headache, nausea, or an injured eye changes the level of concern. A clinician can examine the cornea and pressure inside the eye when needed.

Do not rub the eye. Rinse out loose irritants with clean water, use a cool compress for irritation, and pause contact lenses until the eye is comfortable and medically cleared. Do not share towels, cosmetics, or eye drops. Avoid using leftover antibiotic or steroid drops. More guidance is available under [Red Eye](/symptoms/red-eye/).

Seek urgent assessment for reduced or changed vision, moderate or severe pain, marked light sensitivity, an eye injury, chemical exposure, a foreign body that will not rinse out, or redness with nausea and headache. Contact-lens wearers should seek prompt advice for painful redness because corneal infection can worsen quickly.

Ask whether the redness fits irritation, allergy, infection, or another eye problem; whether you should stop lenses; and which drops are safe. Mention discharge, itching, pain, vision changes, injury, and the time the redness began.