What Is Pink Eye?


Conjunctivitis, also known as pink eye, is an eye condition caused by infection, allergy or irritants. It is commonly known as ‘pink eye’ because it causes the white of the eye to turn pink or red. As well as this, it can affect both eyes and cause them to burn, produce pus, itch and water.1

Although conjunctivitis can be uncomfortable, it rarely affects your vision and can be easily treated without medication. However, if your symptoms are severe, your eye doctor may prescribe you certain medications depending on the cause of the infection. 

This article will tell you everything you need to know about conjunctivitis including the causes and symptoms as well as the management and treatment options. 

Causes of pink eye

Pink eye is caused by inflammation of the transparent membrane called the conjunctiva that lines the eyeball and eyelid. This then causes the small blood vessels in the conjunctiva to become swollen and irritated which makes them more visible and causes your eye to turn red or pink in colour.1

Pink eye is most commonly caused by a viral infection but it can also be caused by a bacterial infection or an allergic reaction.1

Other causes include:2

  • Chemicals in the eye
  • A foreign object in the eye
  • A blocked or incompletely opened tear duct (in newborns)
  • Fungi
  • Ameba and parasites
  • Indoor and outdoor air pollution - caused by smoke, fumes, dust or chemical vapours
  • Wearing contact lenses

Viral and bacterial conjunctivitis

Up to 90% of viral conjunctivitis cases are caused by adenovirus and therefore it is the leading cause of infectious conjunctivitis worldwide. Viral conjunctivitis can also be caused by other viruses such as HSV infection and varicella-zoster virus.1

Although bacterial conjunctivitis is less common than viral conjunctivitis, it is more common in children than adults. Bacterial conjunctivitis usually results from direct contact with an infected individual and results from infection by certain bacteria such as Staphylococcus aureus, Streptococcus pneumoniae or Haemophilus influenzae. As well as this, wearing contact lenses that are not clean or are not your own can also cause bacterial conjunctivitis.2

Both bacterial and viral conjunctivitis can occur along with symptoms of a cold or respiratory infection such as a sore throat. They are both highly contagious and can be spread through direct or indirect contact with eye discharge from an infected person.2

Allergic conjunctivitis 

Allergic conjunctivitis can affect both eyes, including the eyelids and cornea, and is caused by an allergy-causing substance such as pollen, mould, dust mites, medicines or cosmetics. If you are allergic to these substances, your body will produce an antibody called immunoglobulin E (IgE). This antibody triggers special cells found in the mucus lining of your eyes and airways to release histamines. Histamines are inflammatory substances that cause multiple allergy symptoms including red or pink eyes. Allergic conjunctivitis can also trigger inflamed, itchy and watery eyes as well as other allergy symptoms such as sneezing and a runny nose.1,3

Unlike bacterial and viral conjunctivitis, allergic conjunctivitis is not contagious and occurs more frequently in people with allergic conditions such as hay fever, asthma and eczema. Allergic conjunctivitis can occur both seasonally, such as when the pollen count is high, or throughout the year as a result of indoor allergens such as dust mites and animal dander.1

Signs and symptoms of pink eye

Conjunctivitis can affect both eyes and symptoms include:

  • Redness - the whites of the eye are pink or red in colour
  • Itching, irritation or burning
  • Swelling of the conjunctiva
  • Watery eyes
  • Eye discharge (pus or mucus) that sticks to the lashes
  • Feeling like there is something in your eye or you have the urge to rub your eye
  • A gritty feeling in your eyes
  • Light sensitivity in one or both of your eyes

Management and treatment for pink eye

Treatment for conjunctivitis depends on your symptoms and if it is caused by a virus, bacteria or an allergen. However, to ease your symptoms, you can:

  • Press a cold flannel against your eyes for a few minutes 
  • Wet a clean cotton wool pad with warm water and gently wipe your eyelashes to clean crusts
  • Avoid wearing contact lenses until your eyes are better

Treatment for viral conjunctivitis

Most cases of viral conjunctivitis are mild and do not require treatment. The infection usually clears up on its own in 7-14 days without treatment but some cases may take up to 2 or 3 weeks to clear up.2

Since viral conjunctivitis is caused by a virus, antibiotics will not help. However, an eye doctor may prescribe antiviral medication if the infection is caused by more serious forms of conjunctivitis such as herpes simplex virus or varicella-zoster virus.2

Treatment for bacterial conjunctivitis

Bacterial conjunctivitis often clears up without treatment and symptoms can improve in 2-5 days but may take up to 2 weeks to completely go away. However, depending on the severity of your symptoms, your eye doctor may prescribe you antibiotics, usually in the form of eye drops, to help ease symptoms, shorten the length of infection and reduce complications and the spread to others. This may be necessary if:2

  • You have eye discharge (pus)
  • You have a weakened immune system
  • Certain bacteria are suspected to cause infection

Treatment for allergic conjunctivitis

The most effective way of treating allergic conjunctivitis is by removing the allergen from your environment. Your eye doctor may also prescribe you medicines that help relieve your symptoms such as:1

  • Medicines that help control your allergic reactions - antihistamines and mast cell stabilisers
  • Anti-inflammatory medicine - decongestants, steroids and anti-inflammatory eye drops


How is pink eye diagnosed

An eye doctor will diagnose pink eye and whether it is caused by a virus, bacteria or allergen based on:3

  • Symptoms
  • An examination of your eyes
  • Patient history

If your symptoms are severe or your eye doctor suspects a high-risk cause then a sample of your eye discharge may be analysed for further testing. 

How can I prevent pink eye

Here are some ways you can prevent pink eye:3

  • Wash your hands with soap regularly 
  • Use a clean towel and washcloth daily and do not share
  • Wash your pillowcase and face washcloths with warm water and detergent and change them often
  • Throw away old eye makeup e.g. mascara
  • Do not share eye makeup or eye products with other people
  • Do not touch or rub your eyes with your hands

Who are at risks of pink eye

You are at a higher risk for pink eye if:3

  • You have been exposed to someone infected with bacterial or viral conjunctivitis
  • You have been exposed to something you are allergic to e.g. pollen
  • You use contact lenses

How common is pink eye

Pink eye is extremely common and is one of the most common eye infections in both children and adults.3

Is pink eye contagious

Pink eye can be highly contagious and easily spread from person to person in different ways. 

They usually spread through:3

  • Close contact with an infected person e.g. touching or shaking hands
  • Indirect contact - touching contaminated surfaces then touching your eyes
  • The air - coughing or sneezing
  • Using old eye makeup or sharing contaminated eye makeup

When should I see a doctor

You should see a GP or eye doctor if:

  • Your symptoms have not improved after 2 weeks
  • Your baby has red eyes
  • You have eye pain
  • You have blurred or decreased vision
  • You have large amounts of eye discharge
  • You feel like there is something stuck in your eye
  • You wear contact lenses and have spots on your eyelids as well as other conjunctivitis symptoms (you may be allergic to your contact lenses)


In summary, conjunctivitis, also known as pink eye, is an eye condition that causes inflammation of the tissue lining the eyelid. It is most commonly caused by a viral infection (viral conjunctivitis), bacterial infection (bacterial conjunctivitis), allergens (allergic conjunctivitis) or irritants. Both bacterial and viral conjunctivitis are highly contagious and can be easily spread through direct contact with an infected person or indirect contact by touching contaminated surfaces and then touching your eyes. Most cases of conjunctivitis do not require treatment as symptoms usually improve on their own. However, depending on the severity of your symptoms and the cause of the infection, your eye doctor may prescribe your antibiotic eye drops, antiviral medicine, antihistamines or anti-inflammatory eye drops. If you feel your symptoms are severe, for example, you have eye pain, decreased vision, you feel like something is stuck in your eye or you have a baby with conjunctivitis symptoms, you should seek professional care immediately. 


  1. Azari AA, Arabi A. Conjunctivitis: a systematic review. J Ophthalmic Vis Res [Internet]. 2020 Jul 29 [cited 2023 Mar 31];15(3):372–95. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7431717/ 
  1. CDC. Protect yourself from pink eye [Internet]. Centers for Disease Control and Prevention. 2021 [cited 2023 Mar 31]. Available from: http://www.cdc.gov/conjunctivitis/ 
  1. Pink eye (Conjunctivitis) - Symptoms and causes [Internet]. Mayo Clinic. [cited 2023 Mar 31]. Available from: https://www.mayoclinic.org/diseases-conditions/pink-eye/symptoms-causes/syc-20376355 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Suad Mussa

Bachelor of Science – BSc, Biology. Queen Mary University of London

Suad Mussa is a biology graduate with a strong passion for medical writing and educating the public about health and wellbeing.

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