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What is conjunctivitis?

Conjunctivitis is the medical name for inflammation of the conjunctiva; this is the thin layer of tissue on the inside of the eyelids and which also covers the white part of the eye. Commonly known as pink eye, conjunctivitis is often caused by a virus, bacteria, allergies or other non-infectious causes. Conjunctivitis is a common eye condition and is not usually serious.[1][2][3][4][5][6]

General symptoms of conjunctivitis include:[1][2][3][4][5][6]

  • Pinkness or redness of the eye
  • Burning, itching, a sensation of grittiness, or mild pain or discomfort in the eye
  • Discharge from the eye; this may be watery or thick and pus-like, depending on the cause
  • Formation of a crust around the eye from discharge[7]
  • Swollen and/or reddened eyelids

Depending on the type of conjunctivitis, other signs and symptoms may be present. One or both eyes may be affected by conjunctivitis. When only one eye is affected, it is called unilateral conjunctivitis. When both eyes are affected, it is called bilateral conjunctivitis.

Many cases of mild conjunctivitis clear up on their own, without specific treatment. Cleaning the eyes with water and a clean cloth or sterile pad, applying warm or cool compresses and using lubricating eye drops, also known as artificial tears, may help to relieve symptoms. However, medicine such as antibiotics, antiviral medication or allergy medication may be necessary in more serious cases of conjunctivitis.[1][2][3][4][5][6]

Most people make a full recovery from conjunctivitis, and the condition does not typically cause any complications. However, in a small number of cases, conjunctivitis can be very serious, and may cause damage to the eyes if it is not treated effectively. Anyone with severe symptoms should see a doctor immediately. These include:[4][6]

  • Intense pain in the eye
  • Extreme redness in the eye
  • Inability to open the eye
  • Severe sensitivity to light
  • Blurred vision that persists after wiping away discharge

If symptoms are mild but do not go away, medical advice should also be sought.

Furthermore, if conjunctivitis occurs in newborn babies or people with weakened immune systems, such as those who have HIV or are undergoing treatment for cancer, it can be very severe, and medical advice should be sought without delay.

Conjunctivitis can affect people of any age, though bacterial conjunctivitis tends to be more common among children than adults.[4] Bacterial and viral conjunctivitis are highly contagious, which means that the infection can spread easily from one person to another. It is important that a person with infectious conjunctivitis take steps to avoid passing it on to others, such as practising good hygiene.

Diagnosing conjunctivitis

If symptoms are mild, a diagnosis of conjunctivitis can generally be made without seeing a doctor, and the condition can be managed at home. However, if there is any uncertainty or concern over the condition, or the symptoms seem severe, seeing a doctor is very important.

A doctor will take the person’s medical history and examine their eyes to determine whether conjunctivitis is present, and if so, what type of conjunctivitis it is. They will rule out other eye conditions like dry eye syndrome and more serious concerns such as uveitis and keratitis, which is an inflammation of the cornea, the front part of the eye. In some cases, laboratory tests may be necessary to confirm the diagnosis.[1][3][5]

Types of conjunctivitis

There are three main types of conjunctivitis:

Bacterial conjunctivitis

Bacterial conjunctivitis is pink eye that is caused by infection with bacteria, e.g. Staphylococcus aureus and Streptococcus pneumonia, or, less commonly, the bacteria chlamydia and gonorrhea, which are sexually transmitted infections (STIs). Read more about bacterial conjunctivitis, including specific symptoms, treatment approaches including antibiotics, possible complications and prevention strategies.

Viral conjunctivitis

Viral conjunctivitis is pink eye that is caused by infection with a virus, e.g. adenovirus – the group of viruses that cause the common cold, herpes simplex or herpes zoster ophthalmicus. Read more about viral conjunctivitis, including specific symptoms, treatment options including antiviral medication, possible complications and prevention strategies.

Non-infectious conjunctivitis

The third type of conjunctivitis is not caused by bacteria or viruses and is not infectious, meaning it cannot be spread from person to person. There are several different subtypes of non-infectious conjunctivitis. These include:

Allergic conjunctivitis

Allergic conjunctivitis is the most common subtype of non-infectious conjunctivitis/pink eye and is caused by an allergen, e.g. pollen, dust or animal dander. Read more about allergic conjunctivitis, including specific symptoms, types including giant papillary conjunctivitis and vernal keratoconjunctivitis, treatment options and possible complications.

Irritant conjunctivitis

Sometimes mistaken for an allergic reaction, this type of conjunctivitis can be caused by irritation from a variety of substances. These include cosmetic products, soaps, swimming pool chlorine and other commonly used chemicals, smoke, dirt and other objects that may get into the eyes.[1][3][8][9][10]

If the eye suffers physical trauma, for example by being hit or scraped, symptoms of conjunctivitis may also develop.[10] This can be very serious, and a doctor should be seen without delay to prevent complications.

Mild cases of irritant-related conjunctivitis can usually be treated by removing or avoiding the irritating substance, flushing the eyes with water and applying compresses and lubricating eye drops to the eyes. However, more serious cases may require specialist medical treatment.

If symptoms are severe, or the irritant is a toxic substance, e.g. a strong chemical, medical attention should be sought urgently.

Toxic conjunctivitis

This type of conjunctivitis is also often mistaken for an allergic reaction and can be considered a subtype of irritant conjunctivitis. However, toxic conjunctivitis is caused by the use of certain eye care products or eye medications for a long period of time. It most commonly occurs in people with glaucoma.

Toxic conjunctivitis tends to be commonly caused by preservatives in eye medication, contact lens solutions and artificial tears.[11] A doctor can advise on the best treatment approach.

Conjunctivitis in newborn babies

Newborn babies can be affected by various types of conjunctivitis, including viral conjunctivitis and bacterial conjunctivitis, as well as irritant-caused conjunctivitis. Regardless of the cause, pink eye in infants is called neonatal conjunctivitis or ophthalmia neonatorum. Babies with conjunctivitis usually develop puffy, red eyelids and discharge from the eyes within 1-14 days of birth.[4][12]

During the childbirth process, an infant’s eyes may become infected with a virus or bacteria from the mother. In some cases, this may be the bacteria linked to chlamydia and gonorrhea, or, rarely, the viruses that cause oral and genital herpes; herpes simplex 1 and herpes simplex 2.[12][13]

Silver nitrate solution, traditionally administered to a newborn’s eyes to prevent conjunctivitis, can actually cause irritant conjunctivitis. For this reason, many doctors now avoid using silver nitrate and use antibiotic eye drops instead. However, some babies may develop irritant conjunctivitis from the chemicals in these eye drops, too.[12][14][15]

Sometimes, a case of conjunctivitis in a baby is confused with sticky eyes caused by a blocked tear duct. However, a blocked tear duct will not cause the redness or swelling seen in conjunctivitis.[4]

Conjunctivitis in babies can be extremely serious, and any infant showing signs of conjunctivitis should be taken to a doctor immediately. Treatment with antibiotic, antiviral or other medication may be necessary, together with referral to an ophthalmologist.[13]

Conjunctivitis treatment

In many cases, conjunctivitis in adults and children will clear up on its own, without specific treatment. To relieve discomfort, the following home remedies and over-the-counter treatments may be helpful:[1][3][4][16][17]

  • Gently wiping discharge from the eye with a clean cloth, sterile pad or cotton wool soaked in water
  • Applying lubricating eye drops, called artificial tears, which are available without a prescription, to the eye
  • Applying a cold or warm compress – a clean cloth that has been soaked in water – to the eye
  • Avoiding rubbing the eyes, as this may aggravate symptoms
  • Avoiding the use of contact lenses and makeup until the conjunctivitis has cleared
  • In the case of allergic conjunctivitis, avoiding exposure to the allergen, e.g. dust

In serious cases of conjunctivitis, prescription eye drops and other medicine, such as antihistamine tablets – for allergic conjunctivitis, antibiotics – for bacterial conjunctivitis, and antiviral medication – for viral conjunctivitis, may be recommended. Sometimes, a person will be referred to an eye specialist, an ophthalmologist, for treatment.

  1. Southern Cross Medical Library. “Conjunctivitis (pink eye) - symptoms and treatment.” January, 2018. Accessed June 15, 2018.

  2. Association of Optometrists. “Bacterial and viral conjunctivitis.” Accessed June 15, 2018.

  3. National Eye Institute. “Facts About Pink Eye.” November, 2015. Accessed June 15, 2018.

  4. Patient. “Infective Conjunctivitis.” February 24, 2017. Accessed June 15, 2018.

  5. Patient. “Conjunctivitis.” February 24, 2017. Accessed June 15, 2018.

  6. UpToDate. “Patient education: Conjunctivitis (pink eye) (Beyond the Basics).” August 19, 2016. Accessed June 15, 2018.

  7. Amboss. “Conjunctivitis.” April 10, 2018. Accessed July 4, 2018.

  8. Patient. “Allergic Conjunctivitis.” February 28, 2017. Accessed June 16, 2018.

  9. Centers for Disease Control and Prevention. “Conjunctivitis (Pink Eye): Causes.” October 2, 2017. Accessed June 16, 2018.

  10. DermNet NZ. “Irritant or traumatic conjunctivitis.” December, 2015. Accessed June 16, 2018.

  11. UpToDate. “Toxic conjunctivitis.” March 16, 2016. Accessed June 16, 2018.

  12. Centers for Disease Control and Prevention. “Conjunctivitis (Pink Eye) in Newborns.” October 2, 2017. Accessed June 15, 2018.

  13. Canadian Family Physician. “Treatment and prevention of ophthalmia neonatorum.” November, 2013. Accessed June 15, 2018.

  14. Medscape. “Neonatal Conjunctivitis (Ophthalmia Neonatorum).” April 18, 2017. Accessed July 5, 2018.

  15. Johns Hopkins Medicine. “Conjunctivitis in Children.” Accessed July 5, 2018.

  16. Patient. “Infective conjunctivitis.” February 24, 2017. Accessed June 16, 2018.

  17. Centers for Disease Control and Prevention. “Conjunctivitis (Pink Eye): Treatment.” October 2, 2017. Accessed June 16, 2018.