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Eye & EarICD-10: H10.9Affects approximately 6 million people annually in the U.S.

Conjunctivitis

Also known as: Pink Eye, Red Eye, Eye Infection

Conjunctivitis, commonly known as pink eye, is an inflammation or infection of the transparent membrane (conjunctiva) that lines the eyelid and covers the white part of the eyeball. It can be caused by viruses, bacteria, allergens, or irritants. While pink eye can be highly contagious and uncomfortable, it rarely affects vision and is usually easily treatable.

Symptoms

Redness in one or both eyes
Itchiness or gritty feeling in the eye
Tearing or watery discharge
Thick yellow or green discharge that crusts overnight (bacterial)
Swelling of the conjunctiva or eyelids
Sensitivity to light
Blurry vision from discharge

Causes

  • Viral infection (adenovirus most common; highly contagious)
  • Bacterial infection (Staphylococcus, Streptococcus, Haemophilus)
  • Allergic reaction (pollen, dust, pet dander)
  • Chemical irritants (chlorine, smoke, contact lens solutions)

Risk Factors

  • Exposure to someone with viral or bacterial conjunctivitis
  • Allergies (seasonal or perennial)
  • Contact lens use, especially with poor hygiene
  • Weakened immune system

Diagnosis

  • Clinical examination of the eye
  • Assessment of discharge type (watery vs. purulent)
  • Culture of eye discharge for bacterial identification (in severe cases)
  • Allergy testing if allergic conjunctivitis is suspected

Treatment

  • Viral: supportive care, cold compresses, artificial tears (self-limiting)
  • Bacterial: antibiotic eye drops or ointment (erythromycin, fluoroquinolone)
  • Allergic: antihistamine or mast cell stabilizer eye drops
  • Cool compresses to relieve discomfort
  • Avoid wearing contact lenses until infection clears

Prevention

  • Wash hands frequently and avoid touching your eyes
  • Don't share towels, pillowcases, or eye makeup
  • Replace contact lenses and cases as recommended
  • Clean contact lenses properly and don't sleep in them

When to See a Doctor

  • You have intense eye pain, sensitivity to light, or blurred vision
  • Symptoms worsen or don't improve after 24-48 hours
  • You have a weakened immune system or wear contact lenses
  • A newborn develops eye discharge (possible neonatal conjunctivitis—urgent)

Frequently Asked Questions

Related Conditions

Allergic Rhinitis

Respiratory

Dry Eye Syndrome

Eye & Ear

Chickenpox

Infectious

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Medical Disclaimer: This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

Content reviewed against peer-reviewed medical literature and clinical guidelines. Read our editorial standards.