Conjunctivitis in one eye: what to know

Inflammation of the conjunctiva, the clear covering over the white of the eye and inner eyelid, may stay on one side or spread through hand-to-eye contact. Viral or bacterial infection can cause redness and crusting; allergy or irritation can also affect one eye, especially after dust, cosmetics or a foreign particle. One-sided symptoms do not by themselves identify the cause. Pain, blurred vision or marked light sensitivity suggest that another eye problem may need consideration.

Wash hands before and after touching the face, avoid rubbing the eye, and gently remove crusts with clean lukewarm water and a fresh pad each time. Do not share towels, pillows, eye makeup or contact-lens equipment. Stop wearing contact lenses until symptoms have settled and a clinician advises that they are suitable again. A clinician can decide whether supportive care or prescribed treatment is appropriate; do not use another person’s drops.

Arrange prompt medical assessment for significant eye pain, reduced or blurred vision, strong light sensitivity, injury, chemical exposure, a foreign body that will not wash out, or swelling around the eye. Seek urgent help if symptoms are severe or worsening quickly. A GP consultation can help distinguish conjunctivitis from problems affecting the cornea or deeper parts of the eye.

Ask which cause is most consistent with the pattern, whether contact lenses should remain stopped, how long infection-control precautions are needed, and what change should prompt an urgent review.