Bacterial Conjunctivitis

Bacterial conjunctivitis is a purulent infection of the conjunctiva, most common in children, and one of the most common causes of a red eye seen in primary care/community pharmacy.^[1] It is usually self-limited, resolving over 1-2 weeks even without treatment, though a topical antibiotic modestly shortens the course.^[2] The essential first task is not treating the discharge — it is confirming this is simple bacterial conjunctivitis and not one of the sight-threatening red-eye mimics (angle-closure glaucoma, iritis/uveitis, scleritis, keratitis, corneal ulcer) or the two special forms requiring systemic therapy: gonococcal (hyperacute, vision-threatening) and chlamydial conjunctivitis.^[3]

Typical presentation

Purulent discharge, often starting in one eye, with lids crusted shut on waking. Common pathogens: Haemophilus influenzae, Staphylococcus aureus, Streptococcus pneumoniae; Moraxella catarrhalis occurs mainly in children, often with concurrent otitis media.

• Contact lens wear — raises the risk of bacterial keratitis specifically, not just conjunctivitis, which is a more serious, sight-threatening process.
• Neonates — chlamydial or gonococcal conjunctivitis risk from maternal exposure at delivery (ophthalmia neonatorum).
• Sexually active adults — gonococcal or chlamydial conjunctivitis from genital-to-eye autoinoculation.
• Concurrent or recent otitis media in children.
• Ocular surgery, trauma, or chemical exposure.
• Immunocompromise.

Differentiating bacterial, viral, and allergic conjunctivitis, and blepharitis

These four conditions are the most commonly confused causes of a red, irritated eye in community practice. Distinguishing them correctly determines whether the patient needs an antibiotic, supportive care, an antihistamine, or eyelid hygiene — and getting it wrong means either an unnecessary antibiotic or a missed diagnosis.

Bacterial conjunctivitis — purulent discharge with morning crusting. (CNX OpenStax, CC BY 4.0, Wikimedia Commons)

Viral conjunctivitis — marked redness, watery discharge, often with a preauricular node. (Joyhill09, CC BY-SA 3.0, Wikimedia Commons)

Allergic conjunctivitis — itching is the dominant symptom, often with chemosis (conjunctival swelling). (James Heilman, MD, CC BY-SA 4.0, Wikimedia Commons)

Blepharitis — crusting and scale at the lash base; this is an eyelid problem, not a conjunctival infection, though it can cause secondary conjunctivitis. (Imrankabirhossain, CC BY-SA 4.0, Wikimedia Commons)

History

• Onset speed — hyperacute (hours) suggests gonococcal; typical bacterial onset is over 1-2 days; chlamydial is more indolent/subacute.
• Unilateral or bilateral, duration, and progression.
• Discharge character — purulent and reaccumulating rapidly after wiping raises concern for gonococcal disease.
• Sexual history and contact history in adults with a subacute or hyperacute presentation.
• Contact lens wear, and any recent trauma or chemical exposure.

Examination

• Best corrected visual acuity (with pinhole if glasses are unavailable).
• Inspect lids, conjunctiva, sclera, and cornea; fluorescein staining if corneal involvement is possible.
• Palpate for preauricular lymphadenopathy.
• Consider culture/Gram stain and gonococcal/chlamydial nucleic acid testing for: neonatal conjunctivitis, hyperacute or copiously purulent presentations, contact-lens-related infections, recurrent or treatment-unresponsive cases, or any case with a relevant sexual history.

• Preserve eyesight and prevent structural damage to the eye.
• Control and prevent spread of infection.
• Provide symptomatic relief.

• Stop wearing contact lenses until fully resolved; reassess fit and hygiene before resuming.
• Fastidious hand hygiene, separate towels, and stay home from school/work for 24 hours after starting an antibiotic (or until resolution if untreated).
• Warm compresses 2-3 times daily for 5-10 minutes, followed by gentle lid cleaning to remove crusting.
• Discard any potentially contaminated eye makeup or contact lens solutions used during the infection.

Neonates

Ophthalmia neonatorum (neonatal conjunctivitis) is usually chlamydial or gonococcal and requires urgent same-day referral and systemic treatment; it can also result from chemical toxicity from prophylactic medication instilled at birth. Timing of onset can hint at the cause: chemical (day 1), gonococcal (days 2-5, hyperacute and severe), chlamydial (days 5-14, more indolent) — but this pattern is not reliable enough to withhold urgent evaluation.

Pregnancy/breastfeeding

Topical ophthalmic antibacterials have minimal systemic absorption. For gonococcal/chlamydial conjunctivitis requiring systemic treatment, azithromycin is generally preferred over doxycycline in pregnancy.

Contact lens wearers

Any suspected corneal infiltrate or ulcer in a contact lens wearer is a red flag requiring urgent referral, not routine conjunctivitis management — this reflects a more serious process (bacterial keratitis) than conjunctivitis alone.

Children

Bacterial conjunctivitis is more common in children and is often associated with concurrent otitis media. Fluoroquinolones and prolonged antibiotic courses should be used cautiously and per product labelling.

If there is no improvement after 3-5 days of topical therapy (or no improvement at all if untreated), refer to an ophthalmologist. Chronic, unilateral conjunctivitis should be referred for investigation of a retained foreign body or nasolacrimal duct obstruction, which can act as a bacterial reservoir. Gonococcal and chlamydial conjunctivitis require follow-up of systemic treatment response and confirmation that sexual partners have been evaluated/treated.

1. Reconfirm the diagnosis — reassess for a red-eye mimic (keratitis, iritis, scleritis, angle-closure glaucoma) rather than assuming treatment failure.
2. Check adherence to the prescribed regimen.
3. Reconsider gonococcal or chlamydial conjunctivitis if not already tested for, particularly in a sexually active adult or any case not responding to standard topical therapy.
4. For presumed bacterial conjunctivitis not improving after 3-5 days, refer for culture and ophthalmology assessment.
5. For recurrent unilateral conjunctivitis, refer to investigate nasolacrimal duct obstruction or a retained foreign body.

• Treating gonococcal or chlamydial conjunctivitis with topical antibiotics alone — both require systemic therapy.
• Missing gonococcal conjunctivitis by not recognizing the hyperacute, copiously and rapidly reaccumulating purulent discharge pattern as distinct from typical bacterial conjunctivitis.
• Using an ophthalmic corticosteroid or antibiotic/corticosteroid combination without specialist supervision — can worsen undiagnosed herpetic or fungal keratitis.^[5]
• Missing a red-eye mimic (angle-closure glaucoma, iritis, scleritis, keratitis) by assuming every red eye with discharge is simple bacterial conjunctivitis.
• Not evaluating/treating sexual partners when gonococcal or chlamydial conjunctivitis is diagnosed.

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

Topical antibacterials — typical bacterial conjunctivitis

Systemic therapy for gonococcal and chlamydial conjunctivitis

Topical therapy alone is inadequate for either of these — systemic treatment is required, alongside STI evaluation and partner treatment.