Eye infection: symptoms and treatments

Eye infection, also called conjunctivitis, is characterised by a red eye, weeping, crusting and irritation. Bacteria and viruses are the most common causes of eye infections. Fungal or parasitic infection is rare but can be serious.

In most cases, an eye infection clears up on its own, although in some cases, the condition can be more severe and needs a GP or eye doctor assessment. Eye infections may need to be treated with antibiotic eye drops or ointment.

Eye infection signs and symptoms

An eye infection can occur in one or both eyes. Signs and symptoms of an eye infection may include:

• Redness
• Itching
• Swelling
• Discharge
• Pain
• Problems with vision
• Watery eyes

Eye infection treatment

Mild eye infections often go away within a couple of weeks, do not affect the eyesight and don’t need medical treatment. Bathing your eyes in cool boiled water and maintaining good eye health helps your body get rid of the eye infection. However, in some cases, your pharmacist might suggest eye drops for an eye infection or recommend you see your GP for antibiotics. If your doctor suspects the infection is particularly severe or has spread to other parts of your body, your doctor may prescribe oral antibiotics.

Potential eye infection treatments include:

• Over-the-counter eye ointment or eye drops 
• Eye drops containing antibiotics
• Oral antibiotics
• Antihistamines to settle an allergy
• A saline solution (saltwater) eye bath
• A cool compress to soothe irritation
• Avoiding the trigger (e.g. allergen or source of irritation)

Newborns or children under two should always be seen by a doctor or ophthalmologist for any eye problems or suspected eye infections

Eye infection causes

Eye infection results from a virus, bacteria or fungus (or in some cases, a parasite) entering the eye. Bacterial or viral infections are spread easily by someone with a contagious eye infection.

A widespread viral infection, like coronavirus or a common cold, can also affect the eyes.

Infection can take hold in different parts of the eye:

• The conjunctiva on the eye’s surface (conjunctivitis)
• The inside of the eye (endophthalmitis)
• The middle layer of the eye called the uvea (uveitis)
• The cornea (keratitis)
• The eyelids (blepharitis)
• The tissues around the eyes (cellulitis)

Uveitis is most common in people with immune system problems, including autoimmunity (Source: NHS).

Eye infections may be associated with:

• Contact lenses
• Allergic reaction (can cause allergic conjunctivitis)
• Chemicals like chlorine or bleach
• Eye injury
• Make-up

Less commonly, eye infection can be due to:

• Surgery, including a side effect of glaucoma surgery (Source: JAMA)
• Some sexually transmitted infections, including gonorrhoea, chlamydia and herpes simplex
• Early-stage Lyme disease can cause conjunctivitis (Source: The American Journal of Medicine)

You are also at increased risk of eye infection if you have some health conditions, like autoimmunity or a weakened immune system.

The acanthamoeba parasite is found in soil and water worldwide and can cause a serious eye infection called acanthamoeba keratitis (Source: CDC). Although relatively rare, this eye condition is more common in people who wear contact lenses. Symptoms can include blurred vision, eye pain, redness, a feeling of something in the eye, light sensitivity and watery eyes. The eyes may also have a cloudy appearance (Source: CDC). People with a compromised immune system or some other health conditions are at risk of the acanthamoeba spreading to other parts of the body. Always see your GP or eye doctor if you are concerned or have an eye infection that doesn’t get better.

Bacterial eye infections

A bacterial eye infection, also called bacterial conjunctivitis, is contagious and easily spread through coming into contact with someone with an existing infection. The most common types of bacteria that cause eye infections are streptococcus and staphylococcus.

Some bacterial eye infections can be severe. Trachoma is an infection in both eyes caused by the chlamydia trachomatis bacterium that can lead to blindness (Source: American Academy of Ophthalmology). Trachoma scarring causes the eyelashes to turn inwards, scratching the cornea and leading to corneal ulcers and vision loss.

Signs and symptoms of a bacterial infection include a red or pink appearance (red eye or pink eye), sticky discharge, crustiness and itchiness.

In some cases, bacterial infection can spread to the soft tissue around the eyes, for example from the sinuses, causing cellulitis. This is potentially very serious and needs urgent medical attention.

The bacteria can also enter the eyelids, causing swelling and redness (blepharitis).

Bathing the eyes in cooled boiled water may help, or your GP may prescribe antibiotic eye drops to treat a bacterial eye infection. Avoid wearing contact lenses or eye make-up if you have an eye infection. Resist the urge to rub your eyes, as this can cause ocular irritation and increase the risk of spreading it to others.

Viral eye infection

Viral eye infection (viral conjunctivitis) is most often due to a virus that causes the common cold. However, some viral infections are more serious. The herpes simplex virus (responsible for cold sores) can enter the eye and cause a potentially serious eye infection that could threaten vision. Symptoms include eye pain, swelling, light sensitivity and blurred vision. Herpes simplex typically infects one eye and can be treated with antiviral eye drops or tablets (Source: NHS).

Fungal eye infection

Fungal eye infection typically affects the cornea (mycotic keratitis) and is rarer than bacterial or viral infection. This type of eye infection commonly results from an eyeball injury made by a plant, like a thorn or stick, as it comes from a fungus that lives on plant life. For this reason, people who contract a fungal infection after an eye injury often work outdoors around plants (Source: Science Direct).

Other possible causes of fungal eye infection include corneal transplant surgery, inadvertently introducing the fungus into the eye through an injection or the use of contaminated products like contact lens solution or dye used for procedures (Source: CDC).

Frequently asked questions