What is conjunctivitis?

Conjunctivitis is a medical term for inflammation of the “conjunctiva.” The conjunctiva is a thin, transparent layer of tissue that lines the inner eyelids and outer surface of the eye. While conjunctivitis is more common in children, it can also happen in adults. Conjunctivitis is also called “pink eye” or "red eye."

Conjunctivitis can be acute or chronic depending on the cause of the condition, the symptoms involved, and how long it lasts. Acute conjunctivitis usually goes away in a few days, while chronic conjunctivitis can last much longer, or come back again and again.

Conjunctivitis usually does not cause permanent vision problems. However, in rare cases, it can cause damage if symptoms are severe and are not properly treated.

What causes conjunctivitis?

In most cases, conjunctivitis is caused by a viral infection, usually from the adenovirus. Viral conjunctivitis is most likely to happen after a cold, flu, or other upper respiratory infection, but it can happen any time. Viral conjunctivitis is extremely contagious, and spreads easily among children at school or in daycare.

Another common cause of conjunctivitis is allergies. These can include seasonal allergies or reactions to household allergens such as pet dander, dust, and mold spores.

Other causes of conjunctivitis include:

  • Bacterial infection - This is usually caused by staphylococcus or streptococcus bacteria. Similar to viral conjunctivitis, this form is most likely to happen after a viral illness such as a cold or flu.
  • Environmental toxins or chemicals, such as certain preservatives used in contact lens solutions
  • Sexually transmitted diseases – Conjunctivitis can be caused by infections from chlamydia or gonorrhea. In adults, chlamydia and gonorrhea are sexually transmitted diseases, but babies can also be born with these conditions. This can happen when a mother who has the infection spreads it to her baby during delivery. Conjunctivitis is a very dangerous condition in newborn babies and, in some cases, can cause blindness.

What are the symptoms of conjunctivitis?

Symptoms can be different depending on the type of conjunctivitis. They can affect one or both eyes.

In general, people with conjunctivitis might experience some or all of the following eye symptoms:

  • Discharge – This might be watery or contain pus.
  • Redness and irritation
  • "Matting" of the eyelids – This happens when a crust forms on the lashes overnight, making it difficult to open the eyes when waking in the morning.
  • Sensitivity to light
  • Pain – This might be mild or severe. Some people with conjunctivitis have no pain.
  • Itchiness
  • Burning
  • Foreign body sensation – This is when it feels like an object is stuck in the eye but there is nothing inside.

How is conjunctivitis treated?

Treatments depend on the type of conjunctivitis. Common treatments include ointments, eye drops and cold compresses to help relieve symptoms. Most types of conjunctivitis will get better in one to two weeks with treatment.

Treatment of conjunctivitis caused by allergies or environmental toxins usually involves removing the agent that triggers the symptoms. If you have conjunctivitis caused by allergies, this might mean avoiding pollen, pet dander, or other allergens. If you have conjunctivitis caused by toxins, this might mean switching to a different contact lens solution. People with allergic conjunctivitis might also be given antihistamines to help with symptoms.

Adults with conjunctivitis caused by chlamydia are usually treated with medications in pill form as well as ointments and eye drops. Treatment for this type of conjunctivitis might last for several weeks.