Condition library

Eye infections and contagious red eye

Infectious and contagious conditions of the eye surface, eyelids and surrounding tissues.

Clinically reviewed · Last reviewed 2026-06-13

Conjunctivitis Red, irritated eyes from infection or allergy; the cause guides treatment — viral, bacterial and allergic types need different approaches. Viral conjunctivitis Very contagious watery pink eye, often after a cold; antibiotics do not help — hygiene and time are the main treatment. Bacterial conjunctivitis Sticky yellow-green discharge and glued lids, often needing antibiotic drops after assessment; more urgent in babies and contact-lens wearers. Eye allergies Itchy, red, watery eyes from pollen, dust or pets; seasonal peaks in spring and summer respond well to trigger avoidance and allergy drops. Trachoma A leading infectious cause of blindness worldwide, spread by contact and flies; preventable with hygiene and WHO programmes. Onchocerciasis (river blindness) A parasitic eye disease spread by black flies; a WHO-targeted cause of preventable blindness in affected regions. Endophthalmitis Severe infection inside the eye after surgery or injury; a sight-threatening emergency. Orbital cellulitis Deep infection around the eye causing painful swelling and often fever; a medical emergency. Dacryocystitis Infection of the tear sac causing a painful, swollen lump by the nose; needs antibiotics. Herpes eye infection A cold-sore virus infection of the cornea causing a painful red eye; needs prompt antiviral treatment. Shingles in the eye Shingles affecting the eye area can threaten sight; the rash and eye pain need urgent specialist care. Fungal eye infection A rare but serious corneal infection, often linked to contact lens wear or eye injury; needs urgent specialist care. Acanthamoeba keratitis A rare but serious corneal infection linked to contact lenses and water exposure; painful red eye needs urgent specialist care. Corneal ulcer An open sore on the cornea, often from infection; a sight-threatening emergency needing urgent care. Blepharitis Inflamed eyelid margins causing crusting, grittiness and red rims; daily lid hygiene is the mainstay of control. Stye A painful red lump on the eyelid, usually from a blocked infected lash follicle; warm compresses help most cases settle. Chalazion A usually painless lump in the eyelid from a blocked oil gland; most clear with warm compresses. Episcleritis A mild, usually painless red eye from surface inflammation; different from the more painful scleritis.

Frequently asked questions

Is pink eye always bacterial?

No. Most pink eye is viral or allergic. Antibiotics help only when a clinician thinks bacteria are likely.

When is a red eye an infection emergency?

Severe pain, light sensitivity, reduced vision, a contact-lens-related red eye, or painful swelling with fever need urgent assessment.

How do I avoid spreading conjunctivitis?

Wash hands often, avoid sharing towels and pillows, and keep children home while eyes are very red and watery if local guidance advises.

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