Infectious Conjunctivitis

Infectious Conjunctivitis

Infectious Conjunctivitis

There are two main types of conjunctivitis, based on what has caused the condition - an infection or an allergy.

Conjunctivitis can also be caused if an irritant such as a chemical, or a foreign body such as a piece of grit, gets into your eye.

Types of conjunctivitis

Infective conjunctivitis

Infective conjunctivitis is caused by infection of your eye with bacteria or a virus.

Sometimes babies develop conjunctivitis in the first few weeks after they are born. This can happen if an infection is passed from the mother's cervix (neck of her womb) or vagina during delivery, or if the baby has a reaction to a treatment applied to his or her eye. Contact your GP if your newborn baby has signs of an eye infection.

Allergic conjunctivitis

Allergic conjunctivitis can be caused by an allergy, such as an allergy to pollen (hay fever), house dust mites or cosmetics.

There are four types of allergic conjunctivitis:

seasonal allergic conjunctivitis - this affects both of your eyes and people often get it at the same time as hay fever

perennial allergic conjunctivitis - people with this type of allergic conjunctivitis have symptoms every day throughout the year in both eyes, often on waking each morning

contact dermatoconjunctivitis - this type of conjunctivitis can irritate your eyelids and it occurs most often in people who use eye drops

giant papillary conjunctivitis - this is common in people who use soft contact lenses, although it can also occur in people using hard contact lenses and after eye surgery

The different parts of the eye

Causes of conjunctivitis

Infective conjunctivitis

Viruses are thought to be a more common cause of conjunctivitis than bacteria. The type of virus that usually causes the condition is called an adenovirus. This virus can also cause the common cold, so you may develop conjunctivitis at the same time as having a cold.

Common causes of bacterial conjunctivitis include the bacteria Staphylococcus aureus and Streptococcus pneumoniae. You can catch infective conjunctivitis from being in close contact with another person who has it. It's important to wash your hands after coming into contact with someone who has the condition.

Infective conjunctivitis is most common in children and older people.

Allergic conjunctivitis

You might develop allergic conjunctivitis if you're allergic to plant pollens that are released into the air at around the same time each year. This is called seasonal allergic conjunctivitis or hay fever conjunctivitis.

Perennial (all year round) allergic conjunctivitis can be caused by house dust mites or animal fur.

Eye drops, cosmetics, and other chemicals can also cause allergic conjunctivitis - eye drops are the most common cause.

You can get a form of allergic conjunctivitis called giant papillary conjunctivitis if you use contact lenses, or after eye surgery.

Irritants

Foreign bodies, such as an eyelash or a piece of grit, or chemicals, such as chlorine, getting in your eye can cause conjunctivitis. Conjunctivitis caused by a foreign body may only affect one of your eyes.

Diagnosis of conjunctivitis

Your GP will ask about your symptoms and examine you. He or she may also ask you about your medical ...