Conjunctivitis can result from many causes, including viruses, bacteria, allergens, contact lens use, chemicals, fungi, and certain diseases.

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Schools should allow infected children to remain in school once any indicated therapy is implemented, except when viral or bacterial conjunctivitis is accompanied by systemic signs of illness. However, infected students should refrain from attending school if their behavior is such that they cannot avoid close contact with other students.

Viral Conjunctivitis


Colorized transmission electron micrograph of adenovirus.( Public Health Image Library)

The following viruses can cause viral conjunctivitis, with adenoviruses being one of the most common causes:

AdenovirusesRubella virusRubeola (measles) virusHerpesviruses, includingHerpes simplex virusVaricella-zoster virus, which also causes chickenpox and shinglesEpstein-Barr virus, which also causes infectious mononucleosis (mono)Picornaviruses, such as coxsackievirus A24 and enterovirus 70 (which has caused outbreaks in other countries)

Viral conjunctivitis is highly contagious. Most viruses that cause conjunctivitis spread through hand-to-eye contact by hands or objects that are contaminated with the infectious virus. Having contact with infectious tears, eye discharge, fecal matter, or respiratory discharges can contaminate hands. Viral conjunctivitis can also spread by large respiratory tract droplets. As viral conjunctivitis can be highly contagious, infected individuals should be counseled to prevent transmission e.g., washing hands frequently, using separate towels, and avoiding close contact with others during the period of contagion.

Most cases of acute, infectious conjunctivitis in adults are viral and self-limited; these cases do not require antimicrobial treatment. Antiviral medication may be used to treat more serious forms of conjunctivitis, such as conjunctivitis caused by herpes simplex virus or varicella-zoster virus.

Depending on the cause of viral conjunctivitis, some patients may have additional symptoms or conditions, such as the following:

Common cold, flu, or other respiratory infectionPharyngoconjunctivial fever – a syndrome that can produce conjunctivitis as well as a fever and sore throat, and is most commonly caused by infection with adenovirus serotypes 3, 4, and 7Acute hemorrhagic conjunctivitis – a type of conjunctivitis that is often associated with large epidemics worldwide, especially in the tropical and subtropical regions. The viruses most commonly associated with it include enterovirus 70, coxsackievirus A24, and adenoviruses.Herpetic keratoconjunctivitis – a type of conjunctivitis associated with herpes simplex virus and blister-like lesions on the skin; it may affect only one eyeRubella and rubeola (measles) – conjunctivitis can occur with these viral rash illnesses which are usually accompanied by rash, fever, and cough

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Bacterial Conjunctivitis


Many species of bacteria can cause bacterial conjunctivitis including

Haemophilus influenzaeStreptococcus pneumoniaeMoraxella catarrhalisChlamydia trachomatisStaphylococcus aureusMoraxella lacunataNeisseria gonorrheaNeisseria meningitides

Bacterial conjunctivitis can spread from person to person in many ways. These include from hand-to-eye contact, via eye contact with contaminated objects, through sexual encounters with eye to genital contact, or vertically from mother to baby. Bacteria can also spread by large respiratory tract droplets. Alternatively, changes in the usual bacteria that live on the conjunctiva can also cause conjunctivitis.

Signs and symptoms of bacterial conjunctivitis overlap with other causes of conjunctivitis, including viral and allergic conjunctivitis, which can make diagnosis difficult. Typical signs and symptoms include:

Red eyePurulent discharge that causes eyelids to be matted togetherChemosisDecreased visionEyelid swelling and pain

Contact lens wearers with bacterial conjunctivitis are at higher risk of bacterial keratitis. They should be asked to remove their contact lenses, treated with topical antibiotics, and promptly evaluated by an ophthalmologist.

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Types of bacterial conjunctivitis include:

Acute bacterial conjunctivitis

Is the most common form of bacterial conjunctivitisIn children is often caused by Haemophilus influenzae, Streptococcus pneumoniae, or Moraxella catarrhalisIs typically self-limited within 1–2 weeks, but topical antibiotic therapy may reduce the duration of disease

Hyperacute bacterial conjunctivitis

Is a very rare and severe type of conjunctivitis with rapid onset and progression, as well as severe symptoms, including massive exudate, severe chemosis, eyelid swelling, marked hyperemia, pain, and decreased visionCaused by Neisseria gonorrhoeae or Neisseria meningitidisRequires both parenteral and topical antibiotic therapyCan progress to corneal infiltrates, melting and perforation and vision loss if not treated promptly by an ophthalmologist

Chronic bacterial conjunctivitis

Defined as symptoms lasting for at least 4 weeksCommon causes include by Staphylococcus aureus or Moraxella lacunataOften occurs with blepharitis (inflammation of the eyelid), which can cause flaky debris and warmth along the lidPeople with this condition should see an ophthalmologist

Chlamydial conjunctivitis

In neonatesIt is called chlamydial ophthalmia neonatorum in the first 4 weeks of lifeUsually symptoms develop 5 to 14 days after birth; symptoms can develop earlier if the amniotic sac is ruptured during delivery Concurrent chlamydial infection elsewhere in their bodies (e.g., lungs, nasopharynx) is commonApproximately 50% of infants who develop pneumonia have a history of chlamydial conjunctivitisPresenting symptoms include watery, mucopurulent, or bloody discharge, marked swelling with red, thickened, and friable conjunctivae, and a pseudomembrane may formAmong sexually active peopleAcute disease is commonly unilateral with hyperemia and purulent discharge and caused byChlamydia trachomatissubtypes D through KMany patients will have a mild prolonged coursePresenting with chlamydial conjunctivitis will have an associated genital infectionTrachomaThe leading global cause of preventable blindnessA chronic follicular conjunctivitis caused byChlamydia trachomatissubtypes A through CCauses scarring of the inner eyelid which can cause the eyelashes to turn in and scratch the cornea (trichiasis), leading to permanent damageTransmitted from person to person through contact with discharge from the eyes or nose of an infected person, through shared items, or by flies spreading ocular secretionsRepeat infections occur in children younger than 10 years of ageCommon in developing countries where access to water and sanitation may be poorIs targeted for elimination by the World Health Organization through an innovative, multi-faceted public health strategy known as S.A.F.E. (Surgery to correct the advanced, blinding stage of the disease (trichiasis), Antibiotics to treat active infection, Facial cleanliness and, Environmental improvements in the areas of water and sanitation to reduce disease transmission)

Learn more about trachoma and other hygiene-related diseases.

Gonococcal conjunctivitis

In neonatesInfection usually is acquired during delivery of infants born to mothers with Neisseria gonorrhoeaeIt is called gonococcal ophthalmia neonatorum in the first 4 weeks of lifeIt usually presents in the first 2 days of life and can be associated with bacteremia and meningitisPrompt treatment is recommended as there is concern for corneal perforation, scarring, and blindnessProphylaxis with erythromycin ophthalmic ointment is currently recommended by the U.S. Preventive Services Task Force immediately after birth and is legally mandated in most statesAmong sexually active peopleSymptoms typically develop 24-48 hours following exposure to urogenital secretions containing N. gonorrhoeaeSymptoms include red eyes, thick pus in the eyes, and swelling of the eyelids and conjunctivaGonococcal conjunctivitis in adults is uncommon and treatment data are limited; an infectious disease specialist should be consulted