Understanding Conjunctivitis
Understanding Conjunctivitis

Understanding Conjunctivitis

Conjunctivitis is a common eye condition where the conjunctiva becomes inflamed as a reaction to outside influences, causing it to become sore or irritated. Understand about the causes, signs and symptoms through to the possible treatments in this article.

It is often referred to as ‘pink-eye’ or ‘red-eye’ due to the symptoms caused by the irritation. The condition may affect just one eye, but after several hours both eyes normally show symptoms.

Types of conjunctivitis

There are three main types of conjunctivitis:

  • Infective - This happens as a result of an infection caused by a virus or bacteria.
  • Allergic – This is due to exposure to an allergen, such as pollen. 
  • Irritant – This may occur when an irritant substance enters the eye.

Signs & symptoms

The main symptoms of conjunctivitis are:

-    Red or bloodshot eyes – when the blood vessels in the conjunctiva become inflamed.
-    Watery eyes – when the inflammation causes the conjunctiva’s tear glands to become ‘overactive’.

Infective conjunctivitis can also produce the following symptoms:

  • Your eyes may feel like they are burning.
  • It could feel like you have grit or dirt in your eyes.
  • Your eyelashes may be covered in a sticky coating, particularly in the mornings.
  • The lymph node in front of your ear can become swollen.
  • You may have a pus discharge if the infection is bacterial.
  • You may have a watery discharge if the infection is viral.

If you have allergic conjunctivitis, you may also experience itchy eyes. If you experience eye pain, photophobia, heavily bloodshot eyes, or a disturbance in your eyesight this could be due to a more severe eye condition, such as acute glaucoma, keratitis, or iritis.

If this is the case you should seek immediate medical attention.

Complications of conjunctivitis 

The complications that can arise from conjunctivitis depend on whether it is from an infection or an allergy. 

Complications of infective conjunctivitis 

Bacterial infection can cause a number of complications, especially in prematurely born babies. These can include:

  • Meningitis – When the protective layer surrounding the brain and spinal cord becomes infected.
  • Cellulitis – When a layer of deep skin and tissue gets infected, causing surface skin to become sore.
  • Septicaemia – When bacteria enters the bloodstream and attacks body tissue. 
  • Otitis Media – When the ear becomes infected. It is usually a result of infective conjunctivitis that was caused by Haemophilus influenzae bacteria. Around one in four children are affected by otitis media, however it is a short-term infection.

Babies up to 28 days old can also suffer from dangerous eye infection as a result of infective conjunctivitis, which could lead to permanent eye damage if left untreated. Babies with infective conjunctivitis should be referred to a specialist for examination and treatment – however, complications are not common and most new-borns fully recover.

One in five babies could also contract pneumonia due to infective conjunctivitis that was caused by chlamydia. Pneumonia can be very dangerous to young babies and may require hospital care.

Some forms of conjunctivitis can result in punctate epithelial keratitis, a condition that causes your cornea to swell up. This may lead to:

  • Light sensitivity
  • Pain or discomfort in your eyes
  • In serious cases, your cornea may develop ulcers – if they leave scars these could impair your vision permanently.

You should seek medical attention if you get any irregular symptoms, either from your GP or at the Accident and Emergency department at the nearest hospital.

What causes conjunctivitis?

The three different types of conjunctivitis can have different causes:


This is normally caused by one of three types of infection :

  • Bacterial 
  • Viral 
  • Sexually transmitted – this can be persistent for several months if the root cause, such as chlamydia it is not treated.

The following may put you at higher risk of infective conjunctivitis:

  • Diabetes
  • Infection in your upper respiratory tract (i.e. a cold)
  • A course of corticosteroids
  • Being young or old
  • Blepharitis (inflamed eyelids)

These factors may increase the risk because the above conditions can lead to a weakened immune system. Being in crowded places can also leave you exposed to the infections of others.


Allergic conjunctivitis can come in four forms:

  •  Seasonal allergic conjunctivitis can happen as a result of an allergy to pollen, and can be common in people with other allergies.
  • Perennial allergic conjunctivitis may occur because of dust-mites or flakes of dead animal skin, and can be common in people with other allergies.
  • Contact dermatoconjunctivitis can be caused by make-up , eye drops, or other chemicals you may be allergic to.
  • Giant papillary conjunctivitis can be due to the stitches or prostheses that may be used in eye surgery. It can also be a complication from using contact lenses – roughly 1-5% of soft contact lens users and 1% of hard contact lens users are said to be affected by giant papillary conjunctivitis. 

Allergic conjunctivitis can cause reoccurring symptoms if the root cause is pollen or another allergen you are regularly exposed to – this can cause discomfort and irritation, however it is unlikely to bring on severe or serious problems.


There are a number of possible causes of irritant conjunctivitis, these can include:

  • Shampoo or soap chemicals
  • Smoke
  • Water with chlorine (i.e. swimming pools)
  • Stray objects (i.e. eyelashes)

How your eye works: The conjunctiva

The conjunctiva is a thin layer of cells that line the front of the eye and the inside of the eyelid. It is involved in the production of mucus, as well as some tears – these lubricate the eye and can help remove foreign objects that get trapped.

When you have conjunctivitis the thin layer becomes irritated, causing it to swell up and redden, while making the tear glands overproduce, leaving your eyes sore and watery.

How is conjunctivitis diagnosed? 

Conjunctivitis can normally be diagnosed by your GP when they examine your eyes. Telling your GP about your symptoms and how they started can help them diagnose which type of conjunctivitis it is, enabling them to choose a suitable treatment.

If you aren’t responding to treatment, your GP might recommend more testing. An example of this is a swab test – a small sample of mucus from your eye is sent to a laboratory where they will try to find the cause of the conjunctivitis and decide the treatment. 

How do you treat conjunctivitis? 

Most types of conjunctivitis tend to clear up within one or two weeks, often without needing any medical treatment. If treatment is needed, eye drops or antibiotics will normally be advised depending on what type of conjunctivitis you have. 

Infective conjunctivitis

Most instances of infective conjunctivitis should settle down within a week or two without the need for treatment.

However, there are methods of care you can follow at home:

  • Lubricant eye-drops can help ease any discomfort or soreness. They are generally available over the counter at a pharmacy, but your GP may prescribe them for you. 
  • Taking painkillers (e.g. paracetamol) can ease soreness and symptoms of the flu – they are available over the counter at a pharmacy, however you should only take them if it’s medically safe to do so. 
  • It can help to remove contact lenses until the symptoms disappear – you shouldn’t re-use contact lenses once the condition passes as the infection could still be present. 

If symptoms last longer than two weeks, this is called persistent infective conjunctivitis.

Bacterial conjunctivitis can be treated with antibiotics, such as chloramphenicol or fusidic acid, which are normally in the form eye-drops. However, as the condition will normally clear up on its own, antibiotics are only used if the infection is severe.

Allergic conjunctivitis

The symptoms caused by allergic conjunctivitis can be eased by holding a cool compress or a flannel over your eyes. Removing contact lenses until the symptoms are gone can also help, and you should avoid rubbing your eyes or exposing yourself to allergens (if you can). 

In the case of seasonal or perennial allergic conjunctivitis, your GP might prescribe you antihistamines, corticosteroids, or mast cell stabilisers. 


Antihistamines are used for fast relief of allergies. When the body comes into contact with an allergen, it releases histamines to bring on the symptoms of an allergic reaction – antihistamines stop the histamines from working, thereby preventing the symptoms from appearing. 

They can be administered orally (cetirizine, fexofenadine, loratadine) or as eye-drops (azelastine, emedastine, ketotifen, Otrivine-Antistin). Some of the treatments are only available by prescription, while others can be bought over the counter. 

New antihistamines shouldn’t induce drowsiness, however, they can still cause a sedated feeling. 


In severe cases of allergic conjunctivitis your GP may prescribe corticosteroids in a cream, gel, or ointment – but they are rarely given unless it’s essential. 

Mast cell stabilisers 

Your GP may also prescribe mast cell stabilisers – rather than providing fast relief, they control your symptoms over a long period of time. As they may take a few weeks to have noticeable effect, you may be given antihistamines to take alongside the mast cell stabilisers. They are often prescribed as eye-drops (lodoxamide, nedocromil sodium, sodium cromoglicate).

Giant papillary conjunctivitis

This is normally a result of contact lens use. If you stop wearing the lenses the symptoms may subside. However, if the giant papillary conjunctivitis was caused by recent eye surgery, you should go to the hospital where you can be observed and given treatment.

Irritant conjunctivitis

The symptoms of irritant conjunctivitis should normally subside once the irritant substance has been removed. However, in cases where a harmful substance (e.g. bleach) is involved, you should be taken to the hospital where they will rinse your eyes with a saline solution.