What is the most common cause of conjunctivitis?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: June 26, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

The most common cause of conjunctivitis is viral infection, particularly adenovirus, as stated in the most recent study 1. This is due to the highly contagious nature of viral conjunctivitis, which explains why it spreads easily in schools and workplaces, making it the predominant form of pink eye worldwide. Viral conjunctivitis typically resolves on its own within 1-2 weeks without specific treatment. Management focuses on symptom relief with artificial tears (4-6 times daily) and cold compresses. Patients should avoid touching their eyes and practice good hand hygiene to prevent spreading the infection. Bacterial conjunctivitis, caused by organisms like Staphylococcus aureus or Streptococcus pneumoniae, is less common but may require antibiotic eye drops such as erythromycin or trimethoprim-polymyxin B, typically used 4 times daily for 5-7 days. Allergic conjunctivitis is another common form, triggered by allergens like pollen or pet dander. Some key points to consider in the management of conjunctivitis include:

  • The importance of proper hygiene to prevent the spread of infection, as emphasized in 1 and 1
  • The need to differentiate between primary conjunctival disease and conditions in which conjunctival inflammation is secondary to systemic or ocular diseases, as discussed in 1 and 1
  • The potential for conjunctivitis to be associated with systemic diseases, such as atopy or acute infections like gonorrhea, and the need to address the underlying systemic disease in treatment, as noted in 1 and 1.

From the Research

Causes of Conjunctivitis

  • The most common cause of conjunctivitis is viral, with adenovirus being the most frequent agent 2, 3, 4, 5.
  • Adenovirus accounts for approximately 80% of all cases of acute conjunctivitis 2.
  • Other viruses such as enterovirus and herpes virus are also common causative agents of conjunctivitis 2, 4.
  • Bacterial and allergic conjunctivitis are also possible, but less common than viral conjunctivitis 6.

Transmission and Symptoms

  • Viral conjunctivitis is highly contagious and can be spread through hand-to-eye contact, ocular secretions, respiratory droplets, and contact with contaminated surfaces or medical instruments 3, 5.
  • Symptoms of viral conjunctivitis include watery discharge, hyperemia, chemosis, and ipsilateral lymphadenopathy 3, 5.
  • Pharyngoconjunctival fever is a common manifestation of adenoviral infection, characterized by abrupt onset of high fever, pharyngitis, bilateral conjunctivitis, and periauricular lymph node enlargement 3.

Diagnosis and Treatment

  • Diagnosis of viral conjunctivitis is often based on clinical findings and medical history, but laboratory diagnostics can play an important role in identifying the causative agent 4.
  • Treatment for viral conjunctivitis is mostly supportive, with no specific antiviral therapy available for adenoviral keratoconjunctivitis 5.
  • Topical corticosteroids may be used to reduce inflammation, but their use is generally recommended for severe cases of conjunctivitis due to potential risks associated with long-term use 6.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Viral Conjunctivitis.

Viruses, 2023

Research

Adenoviral keratoconjunctivitis.

Survey of ophthalmology, 2015

Research

Molecular identification of viral agents associated with acute conjunctivitis: a prospective controlled study.

The Brazilian journal of infectious diseases : an official publication of the Brazilian Society of Infectious Diseases, 2017

Research

Management of Adenoviral Keratoconjunctivitis: Challenges and Solutions.

Clinical ophthalmology (Auckland, N.Z.), 2020

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.