Both bacterial and viral pink eye (conjunctivitis) cause similar symptoms. However, bacterial conjunctivitis can produce a thicker discharge and cause pain and swelling.

Bacterial and viral conjunctivitis can be difficult to tell apart. However, people who get viral pink eye have typically either had a viral illness or had recent contact with a person who had a viral illness. This can help healthcare professionals make a distinction.

Both types of conjunctivitis can get better without medical treatment. However, a person may need antibiotic eye drops for bacterial conjunctivitis. Some rarer types of bacterial conjunctivitis can progress rapidly and require urgent treatment.

This article further explains bacterial versus viral conjunctivitis, including their symptoms, causes, and treatment.

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Conjunctivitis, or “pink eye,” is an eye infection that causes inflammation of the conjunctiva, a thin membrane lining the inner surface of the eyelids and the white part of the eyeball. The conjunctiva helps keep the eye moist and acts as a barrier against infections.

However, the conjunctiva itself can sometimes develop an infection. When a virus causes the infection, doctors call it viral conjunctivitis. Several viruses can cause viral conjunctivitis, including:

  • adenovirus, which causes respiratory infections
  • herpes simplex virus (HSV), which can cause cold sores or genital herpes
  • varicella-zoster virus, which causes chickenpox
  • rubeola virus, which causes measles
  • picornaviruses

When a virus infects the conjunctiva and begins to multiply, it can lead to symptoms such as:

  • redness of the eye or eyelids
  • itching and burning
  • tears or watery discharge
  • the feeling of a foreign object in the eye
  • light sensitivity

The most common cause of viral conjunctivitis is adenovirus. People can develop conjunctivitis while they have a common cold. As with most colds, the symptoms usually resolve on their own without treatment. Viral conjunctivitis may take 14–30 days to go away. However, it is typically only contagious for 10-14 days.

Bacterial conjunctivitis occurs when bacteria infect and inflame the conjunctiva. Some people are at greater risk of developing this type of conjunctivitis, including:

  • children
  • older adults
  • people who wear contact lenses
  • people with weakened immune systems

The most common species of bacteria that cause bacterial conjunctivitis in children are:

  • Haemophilus influenzae
  • Streptococcus pneumoniae
  • Moraxella catarrhalis

In adults, the most common species that cause the condition are staphylococcal bacteria. These bacteria can get into the eye through:

  • contact with someone who has bacterial conjunctivitis
  • contact with objects that a person with the condition has used
  • contact with respiratory droplets from coughs or sneezes
  • changes in the bacteria that live on the conjunctiva

The symptoms of bacterial conjunctivitis are similar to those of viral conjunctivitis but can also include:

  • thick green or yellow discharge that causes the eyelids to stick together
  • swelling of the eye surface
  • eyelid swelling and pain
  • decreased vision

The following table compares the characteristics of bacterial versus viral conjunctivitis:

Bacterial conjunctivitisViral conjunctivitis
Causebacteria such as H. influenzae or S. pneumoniaeviruses such as adenovirus or HSV
Distinctive symptomsthick, pus-like discharge that sticks the eyelids togetherthin, watery, clear discharge
Associated conditions• bacterial respiratory infections
• ear infections
• common cold
• other viral illnesses
Duration• usually 1–2 weeks
• less with treatment
14–30 days
Contagiousnesshighly contagioushighly contagious

Viral conjunctivitis usually goes away on its own. As a result, treatment focuses on easing symptoms. Doctors may recommend:

  • keeping the eye clean
  • applying artificial tears to lubricate the eye
  • using cool compresses to reduce discomfort

Antibiotics will not help with viral conjunctivitis, but if a person has a weakened immune system or the infection potentially has harmful effects, a healthcare professional may prescribe an antiviral treatment. For example, conjunctivitis due to HSV can become serious.

Antibiotics can help with bacterial conjunctivitis. If a healthcare professional suspects that the infection is bacterial, they may prescribe topical antibiotic eye drops or ointment. These treatments can help decrease symptoms, speed healing, and reduce the chance of transmission.

A person must finish the entire course of antibiotics, even if symptoms improve before then.

Both types of conjunctivitis are highly contagious. If symptoms are affecting only one eye, it is important to avoid spreading the condition to the other eye or to other people. To safely clean the eye or apply ointment:

  1. Wash hands with soap and water.
  2. Dampen a clean cotton pad with water. Use the pad to gently clean the affected eye.
  3. Use another clean cotton pad to pat the eye dry.
  4. Apply any ointment or eye drops.
  5. Dispose of the used pads and wash the hands again when finished.

Avoid sharing items that touch the eyes, such as towels, face cloths, pillows, or eye makeup, until the infection has completely cleared.

Here are some common questions about bacterial versus viral conjunctivitis.

Is most conjunctivitis viral or bacterial?

Most cases of conjunctivitis are viral. In adults, viruses cause 75% of all cases. Of those, up to 90% of cases are due to adenoviruses.

Is viral worse than bacterial?

Generally, bacterial conjunctivitis is worse than viral conjunctivitis. It often causes a thicker discharge that can make it difficult for a person to see. However, both types can lead to complications under certain circumstances.

There is also a rare form of the condition known as hyperacute bacterial conjunctivitis, which causes large amounts of fluid to come from the eye. It progresses rapidly and requires both topical and IV antibiotics.

How long is conjunctivitis contagious for?

Most cases of viral conjunctivitis are highly contagious for up to 14 days, but the infection can take up to 30 days to clear. During this time, it is possible to transmit the infection.

Conjunctivitis is usually mild and passes on its own. However, if symptoms worsen or do not improve with home care, or if a person who has conjunctivitis also has a compromised immune system, they should contact their healthcare professional for advice.

Call an eye doctor as soon as possible if a person has any of the following eye symptoms:

  • significant eye pain
  • vision problems
  • light sensitivity
  • difficulty opening the eye
  • large amounts of pus or mucus coming from the eyes
  • severe redness or swelling of the eyes

These symptoms could indicate a serious infection or another condition. Prompt diagnosis and treatment can help prevent complications.

Viral and bacterial conjunctivitis cause similar symptoms, including redness, swelling, itching, and discharge. However, viral conjunctivitis usually causes a thin, watery discharge, while bacterial conjunctivitis causes a thicker discharge.

The goal of treatment for viral conjunctivitis is to ease symptoms until the infection clears by itself. Bacterial conjunctivitis sometimes requires treatment with antibiotic eye drops or ointment.

If a person notices any changes in their eye health, such as increasing pain or vision problems, they should contact their healthcare professional for advice.