What should you know about dark red eye?

A sharply defined bright or dark red patch on the white of the eye can be a small surface bleed, sometimes after coughing, sneezing, rubbing, or straining. Diffuse redness with itching and watering can occur with allergic conjunctivitis. Sticky discharge, gritty discomfort, and redness may occur with conjunctivitis. Pain, light sensitivity, blurred vision, swelling, or a pupil that looks different suggests a problem needing prompt examination. Contact lens use, chemical exposure, recent eye surgery, and an injury change the level of concern. A photograph can help show whether the redness is spreading.

Do not rub the eye, share towels, or wear contact lenses while it is red. Rinse promptly with clean running water after a chemical splash and seek urgent advice. A cool compress may soothe irritation. Avoid using someone else’s eye drops, especially drops marketed to hide redness, because they may mask symptoms or irritate the surface. Wash hands before and after touching the area, and arrange an examination if redness does not settle or keeps returning.

Get urgent eye care for severe pain, reduced or blurred vision, marked light sensitivity, an injury, chemical exposure, a protruding eye, or redness with nausea and headache. Seek prompt review for contact-lens-related redness, increasing swelling, thick discharge, or a red eye with fever. A painless red patch without vision change can still be checked if it recurs or does not fade.

Is the redness on the surface or deeper in the eye? Could allergy or infection explain the discharge or itching? Should I stop contact lenses, and which drops are suitable for my symptoms?