Conjunctivitis: Bacterial, Viral and Allergic

  • Infectious or non-infectious Inflammation of the conjunctiva of one or both eyes
    • The conjunctiva is the translucent covering of the sclera (white area) of the eye (bulbar area) and the undersurface of the eyelids (palpebral area)
  •  Infectious causes
    • Bacterial:
      • Children: H. influenzae, S. pneumoniae, S. aureus
      • Adults: S. aureus, coagulase-negative Staphylococcus organisms, H. influenzae, S. pneumoniae
    • Viral – adenovirus (most common), herpes simplex virus, others
  • Non-infectious
    • Allergic – IgE-mediated reaction triggered by seasonal or perennial allergens
    • Others – dry eye, contact lenses, chemical exposure, reaction to ophthalmic medications, trauma, etc.
  • Common complaint – infectious conjunctivitis accounts for 30 to 40% of eye-related medical visits
  • Risk factors for infectious conjunctivitis
    • Exposure to someone infected with active viral or bacterial conjunctivitis
    • Poor contact lens hygiene
    • Contaminated cosmetics
    • Chronic dry eye or blepharitis
    • Immunosuppression
  • Self-limited condition with or without treatment – complications very rare
  • For more information on conjunctivitis, go to:

Signs and Symptoms
  • Itching, redness and discharge primary signs and symptoms





Initial Eye Involvement






Purulent or mucopurulent

Usually unilateral but can present bilaterally







Unilateral or bilateral






Serous or mucoid


*Mucoid – mucus discharge (viscous, sticky, clear, white or yellow); mucopurulent – consisting of mucus and pus; purulent – discharge of pus (thick, green - yellow); serous – clear thin watery discharge

  • Others: foreign body sensation, scratching or burning
  • Uncharacteristic signs and symptoms – consider alternate diagnosis and/or refer
    • Eye pain 
    • Blurred vision
    • Photophobia
    • Colored halos
  • Higher likelihood of bacterial conjunctivitis if
    • Gluey eyes in morning
    • Mucopurulent discharge
    • Age < 6 years
    • Lack of itching or burning sensation
    • Presentation in winter (children)
    • No history of conjunctivitis (adults)
  • Higher likelihood of viral conjunctivitis if:
    • Adult
    • Presentation in summer
    • Associated with upper respiratory infection
  • Higher likelihood of allergic conjunctivitis
    • History of recurring conjunctivitis
    • History of atopy
    • Associated with allergic rhinitis
    • Itchiness prominent feature
    • Follows a seasonal pattern
Differential Assessments

The following conditions may present with signs and symptoms similar to uncomplicated bacterial, viral or allergic conjunctivitis and must be ruled out before proceeding to treatment:

  • Dry eye syndrome – red eye caused by decreased tear production and/or increased moisture loss; gritty, irritated eyes with intermittent excessive tearing and blurred vision; chronic condition
  • Disease-associated: Sjogren’s, rheumatoid arthritis, thyroid disorder
  • Drug-induced: anticholinergics, beta-blockers, oral contraceptives, ophthalmic products
  • Adverse effect of an ophthalmic product
  • Blepharitis – red eye associated with inflammation of eyelids, crusted eyelashes, scant watery discharge; slow onset, chronic condition, may be associated with rosacea ( )
  • Infectious keratitis – inflammation of the cornea caused by bacteria, viruses or fungi, can progress to corneal ulcers; may be rapid onset, loss of visual acuity, photophobia, severe foreign body sensation (cannot keep eye open), may be visible opacities in cornea. Contact lens wearers are at higher risk ( )
  • Iritis / uveitis - Inflammation of the anterior uveal tract is called iritis or anterior uveitis; red ring around iris (ciliary flush); different sized pupils: no foreign body feeling, usually no discharge.  (
  • Corneal abrasion from foreign body – history of trauma to eye (
  • Subconjunctival hemorrhage – defined areas of redness in the sclera (white of the eye) caused by hemorrhaging from the blood vessels under the conjunctiva: asymptomatic; benign, resolves in 1 to 2 weeks ( )
  • Angle-closure glaucoma – may present with conjunctival redness. Differentiating symptoms may include decreased vision, halos around lights, severe eye pain, headache, nausea and vomiting. Cornea may appear hazy. (


When to Refer

Patients with the following signs and symptoms may have more serious or complicated conditions and should be referred (doctor, nurse practitioner or optometrist):

  • Decrease in visual acuity - iritis, keratitis, corneal ulcer, acute glaucoma
  • Severe photophobia - iritis, keratitis, corneal ulcer, acute glaucoma
  • Severe foreign body sensation that prevents the patient from keeping eye open
  • Moderate to severe pain - iritis, keratitis, corneal ulcer, acute glaucoma
  • Rash +/- vesicles on eyelids, around eyes – possible herpes simplex or zoster
  • Irregular pupil(s) – fixed, larger or smaller – iritis, glaucoma
  • Ciliary flush especially if unilateral – iritis, glaucoma
  • Severe headache with nausea - glaucoma
  • Hyper-purulent discharge (copious amounts of thick yellow-green pus) with very rapid onset  – gonococcal conjunctivitis
  • Visible corneal haze or opacities – keratitis, iritis, glaucoma
  • Focal rather than diffuse redness
  • Contact lens wearer – higher risk of infection, corneal ulceration

1) Non-pharmacologic

  • Avoid contact lens use until symptoms have resolved
  • Discard any eye drop bottles used during infection
  • No-tears baby shampoo (weak solution with warm water) can be used to cleanse crusts from eyelashes

A) Bacterial

  • Warm compresses to unstick eyelids in morning
  • Irrigate with sterile saline or eye wash to remove secretions and provide relief

B) Viral

  • Cold compresses to relieve irritation, redness

C) Allergic

  • Allergen avoidance if possible
  • Avoid rubbing eyes
  • Sunglasses reduce exposure outdoors
  • Cold compresses over eye to relieve pruritus, swelling


2) Pharmacologic – OTC options

Lubricating drops or ointments for all types

A) Acute Bacterial

  • Polymyxin B-gramicidin eye drops, 4-6 times per day for 7-10 days

B) Viral

  • Antihistamines / decongestant eye drops may provide symptom relief

C) Allergic

  • Antihistamines / decongestant eye drops
    • Appropriate for short-term use (<2 weeks)
  • Mast cell stabilizer drops – not for acute symptoms
  • Systemic antihistamines useful, but less effective than topical

D) Adverse effects

  • Minor (all) - stinging on instillation
  • Serious (decongestants) - pupil dilation, angle-closure glaucoma in predisposed persons, e.g., elderly Caucasian or Asian females who are significantly hyperopic; positive family history. Overuse can cause rebound redness


3) Pharmacologic treatment – prescription options:

A) Acute bacterial

  • For most adults, topical antibiotics are not necessary – majority are viral infections
  • For children, antibiotic treatment reduces the duration of symptoms, decreases transmissibility of the infection and allows for a quicker return to daycare or school
  • Choice of antibiotic is empiric; no difference in comparative efficacy; choose least expensive, most convenient product
  • Ointment preferred for children; excessive tearing; or if patient unable to administer eye drops

First line:

  • Erythromycin 0.5% ophthalmic ointment 
    • One-half inch (1.25 cm) QID for 5 to 7 days        
  • Trimethoprim-polymyxin B 0.1%-10,000 units/mL ophthalmic drops
    • 1–2 drops q3h x 7 days
  • Tobramycin 0.3% ophthalmic drops or ointment (Children > 1 year)
    • Drops: 1–2 drops q4H, then taper
    • Ointment: 1.25 cm BID to TID
    • Should not be used for longer than 7 days due to risk of ocular toxicity

Second line: Out of scope for minor ailment prescribing

  • Fluoroquinolone ophthalmic products – reserved for contact lens wearers, more severe cases due to concerns about increasing resistance
  • Corticosteroids generally should be avoided due to potential for complications

Adverse Effects:

  • Transient stinging when first instilled
  • Blurred vision (for up to 20 minutes) with ointment use
  • Long term use - corneal epithelial toxicity, allergy and bacterial resistance


B) Viral – no Rx products recommended for uncomplicated conjunctivitis

C) Allergic                          

  • First line – dual action antihistamine/mast cell stabilizer
    • Ketotifen 0.01%, 0.035%  (Children ≥ 3 years old 
      • 1 drop ≤ 3 times daily
    • Olopatadine 0.1%, 0.2%
      • 0.1%:  1-2 drops twice daily (Children ≥ 3 years old)
      • 0.2%:  1-2 drops once daily (Children ≥ 12 years old)
    • Fast onset of action, two weeks to reach maximum effect
  • Second line – mast cell stabilizers
    • Nedocromil  2%
      • 1-2 drops twice daily, approved for use in patients ≥ 3 years old
    • Lodoxamide  0.1%
      • 1-2 drops ≤ 4 times daily, approved for use in patients ≥ 4 years old
    • Slow onset: 5 to 14 days; option for prophylaxis for seasonal allergies – begin therapy 2 to 4 weeks before allergen season
    • Adverse effects – well tolerated, < 1% of patients report adverse effects.

4) Pregnancy

  • Preferred therapy: non-pharmacologic measures, artificial tears
  • Second line: Lack of data on use of pharmacologic agents during pregnancy
    • Antihistamines not expected to cause toxicity
    • Short-term use of decongestants (avoid in 1st trimester)
    • Mast cell stabilizers considered unlikely to be harmful
    • Antibiotics:
      • Polymyxin B/gramicidin, erythromycin, tobramycin low risk
      • Trimethoprim possibly harmful (based on oral administration data)


5) Lactation

  • All recommended products are rated as likely compatible with breastfeeding


General Advice / Monitoring

General Advice

  • Self-limiting condition
  • Bacterial and viral infections are very contagious especially for first 48 to 72 hours
    • Avoid contact with others for 24 to 48 hours after starting treatment
    • Wash hands frequently with soap and water; don’t share personal items
    • Topical antibiotics reduce possibility of bacterial infection transmission after 24 hours; no effect on viral transmission
  • Use of warm or cold compresses, lubricating drops and ointments to relieve symptoms
  • How to instil drops or ointment; how to use with other ophthalmic preparations
  • When to expect symptoms to resolve
    • Bacterial: expect improvement in 1-2 days with treatment
    • Viral: gradually resolves over 1-3 weeks
    • Allergic: resolves when no longer exposed to allergen
    • If no improvement or symptoms worsen, contact a healthcare provider
  • Possible adverse effects
    • Transient stinging when drops instilled - continue medication
    • Contact dermatitis, hypersensitivity reaction (uncommon) - stop medication, contact healthcare provider if severe or symptoms persist
  • Follow-up with patient after providing treatment; ask about symptoms, adverse effects
    • Bacterial – 2 days
    • Viral – 1 week
    • Allergic – 3 days
    • If no improvement, worsening symptoms, refer to optometrist, nurse practitioner or doctor
Detailed information on contraindications, cautions, adverse effects and interactions is available in individual drug monographs in the RxTx - CPS from CPhA, RxTx (internet), Lexi-Comp, AHFS, or other reliable drug monograph references. For comprehensive drug comparisons, see RxFiles charts (
This information should be routinely consulted before prescribing.





Erythromycin 0.5% ophthalmic ointment

One-half inch (1.25cm) QID x 5-7 days

Trimethoprim-polymyxin B 0.1% - 10,000 units/ml drops

1-2 drops q3h x 7 days

Tobramycin 0.3% ophthalmic drops or ointment

Drops: 1-2 drops q4h x 7 days
Ointment: 1.25cm BID to TID x 7 days

Ketotifen 0.01% or 0.035% 1 drop TID
Olopatadine 0.1 or 0.2%

0.1%: 1-2 drops BID
0.2%: 1-2 drops OD

Nedocromil 2% 1-2 drops BID
Lodoxamide 0.1% 1-2 drops QID
Prescribing and Billing Details
  • Fee pseudoDIN 00951102; maximum of 3 claims per year
  • May prescribe sufficient quantity to treat one episode of conjunctivitis.
  • Only products with an official indication from Health Canada for bacterial or allergic conjunctivitis and/or recommended by reputable and reliable guidelines are considered for these guidelines.  Only the active ingredients in the "products" section are approved for pharmacist prescribing. 
Treatment Flowchart
Pharmacist Assessment Documents
References / Suggested Reading
  1. Friesen, A.  Conjunctivitis.  In: RxTx  CTMA [internet]. Canadian Pharmacists Association. Available from: (by subscription). (Available in Saskatchewan through SHIRP (
  2. Jackson WB. Red eye. In: RxTx CTC [Internet]. Canadian Pharmacists Association. Available from: (by subscription). (Available in Saskatchewan through SHIRP (
  3. Trobe, J.  Conjunctivitis.  In: UpToDate. Available at (by subscription).
  4. Ostrovski D. Infectious conjunctivitis. In: Dynamed. Available at (by subscription). 
  5. Allergic conjunctivitis. In: Dynamed. Available at (by subscription).
  6. Yeung, K.  Bacterial conjunctivitis.  In: Medscape.  Available at
  7. Pink eye (conjunctivitis). In: Mayo Clinic. (free access)
  8. Azari AA, Barney NP. Conjunctivitis: a systematic review of diagnosis and treatment. JAMA 2013;310(16):1721-9.
  9. AAO Cornea/External Disease PPP Panel. Conjunctivitis. Available at
  10. Cronau H,  Kankanala, R  Mauger T.  Diagnosis and Management of Red Eye in Primary Care. Am Fam Physician. 2010 Jan 15;81(2):137-144


Written by medSask
Posted Feb 2018; Updated October 2018