A – Z of Illnesses & Conditions

Styes:  External stye is an infection of the glands at the base of the eye lashes or an infection of the sweat glands. External styes form on the outside of the eyelids and can be seen as small red bumps.

Internal styes are infections of the sebaceous glands lining the inside of the eyelids. They also cause a red bump underneath the eyelid with generalised redness and swelling visible on the outside.

A stye – also called a hordeolum – usually only affects one eye, although it's possible to have styes in both eyes or to have more than one stye in the same eye. Your vision shouldn't be affected.

Styes contain water and pus and the bacteria will spread if the stye is forcefully ruptured. Styes are characterised by an acute onset and are usually short in duration (7–10 days without treatment).

You should never attempt to burst a stye yourself. It's not always necessary to see your doctor if you develop a stye. However, you should have a painful external stye checked by your doctor.