Bacterial vs Viral vs Chlamydial vs Allergic Conjunctivitis: Key Clinical Differences

Overview

Conjunctivitis is inflammation of the conjunctiva and is commonly classified into bacterial, viral, chlamydial, and allergic types. Differentiation is primarily based on discharge, itching, conjunctival reaction (papillae vs follicles), associated systemic symptoms, and response to treatment.

---

High-Yield Comparison Table

Feature	Bacterial	Viral	Chlamydial	Allergic
Conjunctival reaction	Papillae (inflammatory response)	Follicles (classically viral)	Follicles (chronic/severe cases)	Papillae (“cobblestone” in chronic cases)
Itching	Uncommon	Mild	Not prominent	Hallmark symptom (often severe)
Tearing	Mild	Watery	Mild–moderate	Increased
Discharge	Purulent (yellow/green)	Watery → slightly mucoid	Mucopurulent	Watery or stringy mucus
Associated symptoms	Occasionally mild fever or sore throat	Preauricular lymphadenopathy, fever, sore throat	May involve cornea → scarring; systemic symptoms	Sneezing, nasal congestion, allergic rhinitis
Laterality	Often unilateral → bilateral	Usually bilateral	Often unilateral, chronic	Usually bilateral
Treatment	Topical antibiotics	Supportive ± antivirals (HSV)	Systemic antibiotics	Antihistamine / mast cell stabilizers
Precautions	Hand hygiene	Highly contagious	Treat partners	Allergen avoidance

<figure style="max-width:100%;margin:1em 0;text-align:center;">

<img

src="https://adultchildeye.com/wp-content/uploads/Conjunctiva_reaction_papillae_follicles-.png"

alt="Conjunctival reaction with papillae and follicles"

style="width:100%;height:auto;object-fit:contain;"

onerror="this.onerror=null;this.src='https://archive.org/serve/https://adultchildeye.com/wp-content/uploads/Conjunctiva_reaction_papillae_follicles-.png';"

/>

<figcaption style="font-size:0.9em;color:#555;margin-top:0.5em;">

Image credit:

<a href="https://adultchildeye.com/our-services/conjunctivitis/" target="_blank" rel="noopener">

adultchildeye.com – Conjunctivitis

</a>

</figcaption>

</figure> image https://adultchildeye.com/wp-content/uploads/Conjunctiva_reaction_papillae_follicles-.png credit https://adultchildeye.com/our-services/conjunctivitis/

1. Bacterial Conjunctivitis

Key clues

• Purulent discharge causing eyelids to stick together (especially in the morning)

• Papillae on conjunctiva

• Mild irritation rather than intense itching

Management

• Definitive:

  • Erythromycin ophthalmic ointment

  • Polymyxin B–trimethoprim drops

  • Fluoroquinolones (e.g., ofloxacin, moxifloxacin) for severe cases or contact lens wearers

• Supportive:

  • Warm compresses

  • Eye hygiene and handwashing

Exam pearl👉 Purulent discharge = think bacterial first

---

2. Viral Conjunctivitis

Key clues

• Watery discharge

• Follicles on palpebral conjunctiva

• Preauricular lymph node enlargement

• Often follows upper respiratory infection

Management

• Supportive care only (most cases):

  • Cool compresses

  • Artificial tears

• Antivirals (if HSV suspected):

  • Acyclovir or valacyclovir

Precautions

• Highly contagious

• Avoid sharing towels, cosmetics, eye drops

Exam pearl👉 Follicles + preauricular nodes = viral

---

3. Chlamydial Conjunctivitis

Key clues

• Chronic unilateral conjunctivitis

• Mucopurulent discharge

• Follicular reaction

• Possible corneal involvement → scarring

• Often associated with genital chlamydial infection

Management

• Definitive (systemic therapy required):

  • Azithromycin (single oral dose) or

  • Doxycycline (7 days)

• Public health:

  • Treat sexual partners

  • Counsel on STI prevention

Exam pearl👉 Chronic conjunctivitis + mucopurulent discharge = think chlamydia

---

4. Allergic Conjunctivitis

Key clues

• Severe itching (most important clue)

• Bilateral redness

• Watery or stringy discharge

• Associated allergic rhinitis

Management

• First-line:

  • Antihistamine / mast cell stabilizer drops (e.g., olopatadine)

• Adjuncts:

  • Cool compresses

  • Oral antihistamines (watch for dry eyes)

• Severe cases:

  • Short-term topical corticosteroids (ophthalmology supervision only)

Exam pearl👉 If itching dominates → allergic until proven otherwise

---

Quick Diagnostic Shortcut (Mnemonic)

“PIFA” for Conjunctivitis

• Purulent → Bacterial

• Itching → Allergic

• Follicles + nodes → Viral

• Atypical chronic → Chlamydial