Conjunctivitis, inflammation of the conjunctiva, the clear membrane covering the white of the eye, is one of the most common causes of a sudden-onset red, watery, or sticky eye. It is usually straightforward to treat, but the correct approach depends on whether the cause is viral or bacterial.
The conjunctiva is a thin, transparent membrane that lines the inner surface of the eyelids and covers the white of the eye. When this membrane becomes inflamed, whether from infection, allergy, or irritation, the blood vessels within it dilate, giving the eye its characteristic red or pink appearance. The inflammation also stimulates excess tear production, causing the eye to water or discharge.
Infective conjunctivitis is usually caused by either a virus or a bacterium. The two forms behave quite differently, and distinguishing between them matters when deciding on treatment.
By far the most common form. Viral conjunctivitis is most often caused by adenoviruses, the same family of viruses responsible for the common cold. It frequently follows a few days after an upper respiratory tract infection, and often begins in one eye before spreading to the other.
The discharge in viral conjunctivitis is typically watery rather than sticky. The eye is red and uncomfortable, and there may be swelling of a small lymph node in front of the ear on the affected side, a useful clinical sign that points towards a viral rather than bacterial cause.
Viral conjunctivitis is self-limiting. It usually resolves on its own within one to two weeks without treatment. There is no antiviral eye drop that is effective against adenoviral conjunctivitis.
Viral conjunctivitis is highly contagious. Avoid touching or rubbing your eyes, wash your hands frequently, do not share towels or pillowcases, and avoid swimming pools until the symptoms have resolved completely.
Less common than viral conjunctivitis, but easily distinguished by its discharge. Bacterial conjunctivitis produces a thick, sticky, yellow or green purulent discharge. The eyelids often stick together in the morning, and both eyes can be affected simultaneously or in quick succession.
Common causative organisms include Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae. In sexually active adults, Chlamydia trachomatis is an important cause of a persistent, often unilateral conjunctivitis that does not respond to standard antibiotic drops.
Antibiotic eye drops or ointment, typically chloramphenicol, available over the counter from pharmacies, are effective and usually clear the infection within five to seven days. Swabbing the eyelids with clean, damp cotton wool before applying drops helps remove the discharge and improves the effectiveness of treatment.
Most cases of uncomplicated bacterial conjunctivitis in adults and older children are suitable for self-treatment with over-the-counter chloramphenicol. Your pharmacist can advise on suitability.
Please seek same-day assessment if you experience significant pain inside the eye, any reduction in vision, marked light sensitivity, a corneal ulcer (a white spot on the coloured part of the eye), or if you are a contact lens wearer and develop a red eye, as contact lens wearers are at higher risk of serious corneal infection. Newborn babies with conjunctivitis should always be seen promptly by a doctor.
This condition is covered in detail in Chris Matthews’ patient guide to watery eyes, including how it is investigated, what a clinic appointment involves, and the full range of treatments available.