Conjunctivitis
Conjunctivitis ("pink eye") is inflammation of the eye's surface membrane with viral, bacterial, and allergic causes that are distinguished by a pattern of findings rather than any single sign, per a 2022 JAMA systematic review.
Symptoms
Redness, discharge, and irritation. Watery discharge with one eye then the other, plus a swollen lymph node or sore throat, points toward viral; thick, mucopurulent discharge with morning eyelid matting points toward bacterial; itching in both eyes points toward allergic.
Causes and risk
Viruses cause most cases in adults. Bacterial and allergic causes are also common; contact lens wear raises the risk of more serious causes that need different management.
How it is evaluated
Diagnosis is clinical, based on the discharge pattern, timing, and associated symptoms described above.
Treatment
Viral and allergic conjunctivitis are managed with supportive or antihistamine/mast-cell-stabilizer drops. A Cochrane review found antibiotic drops shorten a bacterial case by only 1-2 days in most cases, supporting a delayed-prescribing approach -- antibiotics are reserved for contact-lens wearers, marked purulence with pain, suspected sexually transmitted causes, or immunocompromised and newborn patients.
When to seek care
Vision loss, moderate-to-severe pain, light sensitivity, or symptoms in a contact lens wearer need in-person evaluation, since telehealth cannot examine the cornea and these findings can signal a more serious eye condition. Any redness in a newborn needs immediate evaluation.