Communicable & Infectious Disease · Topic 17 of 23
Conjunctivitis — Bacterial vs Viral
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Conjunctivitis — Bacterial vs Viral
Pink eye: inflammation of the conjunctiva, most often bacterial, viral or allergic. The danger is missing a corneal problem that threatens vision.
What you'll see
The discharge tells bacterial from viral; itching means allergic
Viral conjunctivitis (most often adenovirus) often comes with a tender preauricular lymph node (in front of the ear). Common bacterial causes are Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae.
Assess first
Check visual acuity in the first assessment of a red eye
Red flags
In a newborn this suggests gonococcal ophthalmia neonatorum, which can perforate the cornea and blind. It is treated with systemic ceftriaxone — eye ointment alone is not enough.
Treatment
Antibiotic drops or ointment — finish the whole course
Cool compresses and artificial tears
Antibiotics do not help viral conjunctivitisAvoid the trigger + antihistamine eye drops
Remove contact lenses until the infection clears
Erythromycin 0.5% ointment, both eyes, within 24 h of birth
Drug choices
Nursing priorities
Bacterial, viral or allergic?
Discharge and itching sort them — and only two are contagious
| Bacterial | Viral | Allergic | |
|---|---|---|---|
| Hallmark | Thick yellow-green pus, lids matted on waking | Watery discharge, often with a cold | Itching, usually both eyes |
| Contagious | Yes — very | Yes — very | No |
| Precautions | Standard | Contact, for the whole illness | Not contagious |
| Treatment | Antibiotic drops or ointment | Self-limited — antibiotics don't help | Avoid the trigger + antihistamine drops |
Teach your patient
Many school policies return a child with bacterial conjunctivitis after 24 hours of antibiotics. CDC: stay home with systemic signs of illness or when close contact cannot be avoided; follow local school policy.
Pus = bacterial, watery = viral, itchy = allergic. But pain, photophobia or blurred vision is not simple pink eye — notify the provider.
Sources · Clinical Overview of Pink Eye (CDC) · Isolation Precautions Appendix A (CDC) · Gonococcal Infections Among Neonates (CDC STI Guidelines 2021) · Erythromycin Ophthalmic Ointment 0.5% label (DailyMed) · Conjunctivitis (StatPearls) · Clinical Nursing Skills 14.1 Administering Eye Medications (OpenStax) · Follow your facility's protocol for newborn eye prophylaxis.
Conjunctivitis — Bacterial vs Viral
The child has a red, goopy eye. The parent wants antibiotic drops immediately — but if this is viral, antibiotics won't help and you'll miss the real teaching moment about hand hygiene.
Conjunctivitis is inflammation of the conjunctiva, categorized by etiology: bacterial, viral, or allergic. Bacterial conjunctivitis: purulent (yellow-green) discharge, eyelid crusting (especially upon waking), starts unilateral but often spreads bilaterally. Common organisms: Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae (children). Treatment: topical antibiotic drops or ointment (erythromycin ointment for routine cases; fluoroquinolone drops are reserved for contact lens wearers or when corneal involvement is a concern). Viral conjunctivitis: watery or clear discharge, associated with URI symptoms (sore throat, rhinorrhea), preauricular lymphadenopathy, highly contagious (adenovirus is the most common cause). Treatment: supportive only — cool compresses, artificial tears, symptom management. Self-limiting in 1–2 weeks. No antibiotic benefit. Allergic conjunctivitis: bilateral, intense itching is the hallmark, watery discharge, seasonal pattern, associated with other allergic symptoms (sneezing, rhinorrhea). Treatment: antihistamine eye drops, mast cell stabilizers, avoid allergens. Ophthalmia neonatorum: conjunctivitis in the first 28 days of life. Gonococcal ophthalmia neonatorum presents with profuse purulent discharge at 2–5 days of life and can rapidly cause corneal perforation and blindness. Prophylaxis: erythromycin 0.5% ophthalmic ointment applied to both eyes of every newborn within 1 hour of birth (even after cesarean delivery). Chlamydial ophthalmia neonatorum presents later (5–14 days) and requires systemic (not topical) treatment. Contact precautions for bacterial and viral conjunctivitis. Nursing: proper eye drop administration technique (pull down lower lid to form a pouch, instill drop without touching the dropper tip to the eye), hand hygiene education, no sharing of towels or pillows, school exclusion for bacterial conjunctivitis until 24 hours on antibiotics (many schools require this), and vision assessment after resolution of infection.
Key Distinctions
Purulent (yellow-green) discharge = bacterial — treat with antibiotics. Watery/clear discharge = viral — supportive care only. This is the fundamental differentiation and the most tested point. Allergic conjunctivitis is distinguished by itching as the predominant symptom and bilateral presentation. Erythromycin eye ointment prophylaxis for newborns prevents gonococcal ophthalmia neonatorum — this is given to ALL newborns, not just those born to mothers with known STIs. Chlamydial ophthalmia neonatorum requires oral azithromycin or erythromycin — topical treatment is insufficient.
Clinical Pearl
Goopy and green — give antibiotics. Watery and weepy — wash hands and wait. The discharge tells you the treatment.
Knowledge Check
3 quick questions on the must-knows for this topic.
Purulent yellow-green eye discharge points to which type?
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