It is a bacterial infection that affects the glands of the eyelids. It can be located either on the inside or outside of the eyelid.

Symptoms: It appears as a red, painful swelling near the edge of the eyelid, often with a drainage point of pus.

Cause: It is usually caused by the bacterium Staphylococcus aureus, which blocks and infects the sebaceous glands of the eyelids.