Conjunctivitis – Diagnosis, Symptoms, and Treatment

Doctor Nathan LeDeaux, MD

Medically reviewed by Dr. Nathan LeDeaux, MD

Medical Professional

Updated - December 28, 2020

Nathan LeDeaux is an emergency medicine physician at the University of Wisconsin and got his M.D. from Northwestern University in Chicago Illinois.

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What is Conjunctivitis?

Conjunctivitis is an eye condition characterized by inflammation and redness of the conjunctiva, the outer membrane that covers the surface of the eye and the inside of the eyelidConjunctivitis is most often caused by allergies, viruses, or bacterial infection.  Individuals usually experience redness, itchiness, and irritation of the eyes.  

What Causes Conjunctivitis?

Conjunctivitis is simply a term that refers to the inflammation of the conjunctiva.  The conjunctiva is a translucent membrane that lines the front of the sclera (the white of the eye) and inner eyelids.  The bulbar part of the conjunctiva covers the visible part of the sclera and the palpebral part of the conjunctiva covers the inner eyelids.  Environmental allergens (e.g. pollen, animal dander), viruses, and bacterial infection can lead to irritation and inflammation of the conjunctiva which leads to discomfort.  This inflammation also causes blood vessels in the conjunctiva to dilate, ultimately resulting in eye redness (hyperemia) and discharge.  Viral and bacterial conjunctivitis are very contagious.

How Common is Conjunctivitis?

In the United States, an estimated 1% of primary care visits are related to conjunctivitis.  About 70% of individuals with conjunctivitis go to their primary care provider or urgent care.  Advanced cases of the condition may require referral to an ophthalmology specialist, particularly if it does not self-resolve within several days or if first-line treatment with antibiotics is unsuccessful.

Viral infection is the most common cause of conjunctivitis and is more frequent in the summer.  Bacterial infection is the second most common etiology and is responsible for 50% - 75% of cases in children. The most common bacterial organisms include H. influenzae, S. pneumoniae, S. aureus, and Moraxella catarrhalis.  Worldwide, C. trachomatis keratoconjunctivitis is responsible for up to 8% of cases and can lead to blindness if left untreated, this form of conjunctivitis is very rare.  Allergic conjunctivitis is the cause of 15% - 40% of cases and is more common in the spring and summer due to the increased amounts of pollen and plant material in the air.

Signs and Symptoms

The symptoms of conjunctivitis usually depend on the underlying cause.  Bacterial conjunctivitis is normally characterized by a significant amount of purulent discharge at the lid margins throughout the day.  It commonly presents in one eye, but both eyes are occasionally infected.  Individuals with Neisseria gonorrhea infection frequently develop a rapidly progressive and severe conjunctivitis that can threaten eyesight.

Viral conjunctivitis normally causes eye redness, clear or mucous discharge, and burning in one eye.  The second eye usually becomes involved within 24-48 hours.  Individuals may have associated viral symptoms such as fever, body aches (myalgias), diarrhea, and headache.  Patients can develop preauricular lymphadenopathy – swelling and tenderness of the lymph nodes in front of the ear.  Symptoms often worsen for the first 5 days, then gradually improve after 1-2 weeks.

Patients with allergic conjunctivitis usually experience redness, itchiness, and watery discharge in both eyesItchiness and the lack of pus or mucus production is a key distinguishing factor between allergic conjunctivitis and other forms of the disease.  Individuals often have coexisting seasonal allergies, nasal congestion, and rhinorrhea.

All of these forms of conjunctivitis may result in the eyes being stuck closed in the morning with a mild to moderate amount of crust-like buildup attached to the eyelids. 


Conjunctivitis can generally be diagnosed based on a history and physical exam alone. It is more difficult to determine which form of conjunctivitis is present. If your physician suspects bacterial conjunctivitis or if you have recurrent symptoms, specialized testing may be required. Generally, the diagnosis of conjunctivitis is focused on ruling out more severe conditions such as keratitis, iritis, or angle-closure glaucoma.  These later conditions often lead to significant eye pain and loss of vision. They are considered eye emergencies that require urgent ophthalmologic evaluation.

Your doctor will perform a detailed eye examination – this includes eye inspection, pupillary light reflex testing, extraocular movement assessment, visual acuity testing with the Snellen chart, visual field examination, and funduscopic examination.  If your eyes have pus draining from them, your doctor may send a sample to the laboratory for gram stain and culture.  This is normally done in individuals with recurrent or refractory cases of bacterial conjunctivitis.

Conjunctivitis Medication and Treatment

The treatment of conjunctivitis depends on its cause.  Bacterial conjunctivitis is normally treated with topical antibiotic drops or ointments such as:

  • Erythromycin 5 mg/g ophthalmic ointment
  • Trimethoprim-polymyxin B 0.1%-10,000 units/mL drops
  • Ofloxacin 3% drops
  • Ciprofloxacin 3% drops

Children, individuals with poor medical compliance, or those who experience trouble administering eye drops should use ointmentAn ointment may temporarily cause visual blurriness for 20 minutes after administration.  Fluoroquinolones such as ciprofloxacin are preferred in individuals who wear contact lenses due to the increased risk of resistant bacterial infections in those who touch their eyes frequently. Your physician will suggest you throw away your current pair of contact lenses and avoid using lenses for the duration of your antibiotic prescription. 

Viral conjunctivitis has no specific treatment.  Patients may have symptomatic relief with the use of topical antihistamine/decongestants or lubricating agents. In some cases, your physician may give you a prescription for an antibiotic to take if your symptoms do not begin to improve within 3 to 4 days. This method allows time for the body to naturally clear a viral infection but allows you to begin antibiotics if your infection does not resolve. 

Allergic conjunctivitis is normally treated with allergen avoidance and general measures such as the avoidance of eye rubbing, discontinuation of contact lens use during symptomatic episodes, application of cool compresses over the eyes, and use refrigerated artificial tears as needed.

Short term (< 2 weeks) use of topical antihistamine/vasoconstrictor preparations can be beneficial.  These include Naphcon-A, Opcon-A, or Visine-A (naphazoline HCl/pheniramine maleate).  Individuals with more than 2 episodes per month and those with yearly allergic disease often receive one of the following topical agents:

  • Patanol (olopatadine)
  • Alrex (loteprednol etabonate)
  • Lastacaft (alcaftadine)
  • Bepreve (bepotastine)
  • Optivar (azelastine HCl)
  • Elestat (epinastine)
  • Ketotifen (ketotifen fumarate)

These medications have antihistamine and mast cell stabilizing properties.  Antihistamines may worsen symptoms in patients with underlying dry eye disease.  Patients with refractory allergic conjunctivitis are occasionally referred to an allergy specialist for consideration of allergen immunotherapy.



  1. Sheikh A, Hurwitz B, van Schayck CP, et al. Antibiotics versus placebo for acute bacterial conjunctivitis. Cochrane Database Syst Rev 2012; :CD001211.
  2. Erdinest N, Solomon A. Topical immunomodulators in the management of allergic eye diseases. Curr Opin Allergy Clin Immunol 2014; 14:457.
  3. Leibowitz HM. The red eye. N Engl J Med 2000; 343:345.


The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.