Stye

Styes are usually caused by a staphylococcal infection . Staphylococcus bacteria often live on the skin without causing any harm.

External styes

A stye on the outside of your eyelid may be caused by an infection of:

• an eyelash follicle these are small holes in your skin that individual eyelashes grow out of
• the sebaceous (Zeis) gland this gland is attached to the eyelash follicle and produces an oily substance called sebum, which lubricates the eyelash to prevent it drying out
• the apocrine (Moll) gland this sweat gland empties into the eyelash follicle and helps prevent the eye drying out

Internal styes

Internal styes can occur when the meibomian glands become infected. These glands are found on the eyelids andproduce an oily liquid, which makes up part of the tear film that covers your eye.

If the meibomian glands become blocked, a cyst can develop, which can become infected (see below).

Blepharitis

Eyelash follicle infectionscan sometimes be a complication of blepharitis . Symptoms of blepharitis include:

• inflamed (red and swollen) eyelids
• burning or sore eyes
• crusty eyelashes
• itchy eyelids

Blepharitis can be a complication of rosacea (a skin condition that mainly affects the face).