Conjunctivitis
Bacterial, viral and allergic conjunctivitis — diagnosis and treatment
Conjunctivitis is inflammation of the conjunctiva — the clear membrane covering the white of the eye and lining the inner eyelids. It is one of the most common eye presentations in pharmacy and primary care. The three main types — bacterial, viral, and allergic — have distinct features and require different management. The key safety question with any red eye is whether visual acuity is affected — reduced vision requires urgent ophthalmological assessment to exclude more serious causes.
Types of Conjunctivitis
Bacterial conjunctivitis is characterised by mucopurulent (sticky, yellow-green) discharge, usually beginning in one eye and spreading to the other. It is most commonly caused by Staphylococcus aureus in adults and Haemophilus influenzae or Streptococcus pneumoniae in children. It is typically self-limiting but antibiotic treatment shortens the duration and reduces transmission. Viral conjunctivitis — most often caused by adenovirus — produces a watery discharge and is frequently associated with a recent upper respiratory tract infection. It is highly contagious and spreads easily by contact. It does not respond to antibiotics, and patients should be advised to avoid touching their eyes and to wash hands frequently. Allergic conjunctivitis causes bilateral itching, watering, and redness, triggered by allergens such as pollen, dust mites, or pet dander. It is often seasonal and associated with other atopic conditions.
When to Refer
Most cases of conjunctivitis are self-limiting and can be managed in community pharmacy or primary care. Urgent same-day ophthalmology referral is required if: visual acuity is reduced, there is significant eye pain (not just grittiness), the cornea appears hazy or there is a corneal ulcer, the pupil is abnormal, symptoms have not improved after a week of antibiotic treatment, or the presentation suggests a more serious condition such as acute angle-closure glaucoma, uveitis, or scleritis. Neonatal conjunctivitis (in a baby under 28 days) is a notifiable condition and requires urgent paediatric and ophthalmological assessment — Neisseria gonorrhoeae and Chlamydia trachomatis are important causes.
Treatment
Bacterial conjunctivitis: Chloramphenicol 0.5% eye drops every 2 hours for the first 48 hours, then four times daily until 48 hours after symptoms resolve (up to 5 days total). Chloramphenicol 1% ointment three times daily is an alternative. Fusidic acid 1% gel (Fucithalmic) twice daily — preferred for children and useful when drop instillation is difficult. Contact lenses should not be worn during treatment. Viral conjunctivitis: No antibiotic treatment needed. Advise cold compresses, regular handwashing, and avoid contact with others to limit spread. Lubricant drops may help with comfort. Resolves in 1–3 weeks. Allergic conjunctivitis: Topical antihistamine (olopatadine 0.1% twice daily, ketotifen 0.025% twice daily) for acute relief. Mast cell stabiliser (sodium cromoglicate 2% four times daily) for prevention. Systemic antihistamines (cetirizine, loratadine) if other allergic symptoms present. Cold compresses help. This article has been prepared following careful evaluation of NICE CKS Conjunctivitis and current BNF guidance.