What to know about a suddenly red eye

Redness happens when blood vessels on the eye surface widen or become more visible. It may affect one or both eyes. Itching and watering can fit allergic conjunctivitis, while sticky discharge and eyelids stuck together can occur with conjunctivitis. Gritty discomfort may follow dryness or an irritant. A sharply defined red patch without pain can have a different explanation from a painful, light-sensitive eye.

Do not rub the eye. Wash your hands, remove contact lenses, and rinse away a suspected irritant with clean water. A cool clean cloth may soothe itching or irritation. Avoid sharing towels and eye makeup, and do not use another person’s drops. Keep track of discharge, exposure to dust or chemicals, itching, and whether the redness is spreading. More symptom context is available at [Red Eye](/symptoms/red-eye/).

Seek urgent medical care for reduced vision, severe pain, strong light sensitivity, injury, chemical exposure, a very painful contact-lens-related red eye, or pain when moving the eye. Fever with swelling around the eye also needs prompt review. Arrange medical advice for persistent redness or significant discharge; [Conjunctivitis](/conditions/conjunctivitis/) and [Allergic Conjunctivitis](/conditions/allergic-conjunctivitis/) are possible causes but cannot be confirmed from redness alone.

Describe when the redness began, one or both eyes involved, pain, itch, discharge, vision, light sensitivity, injury, chemical exposure, and contact-lens use. Ask whether you need examination, isolation precautions, or specific drops.