Possible causes:
- Hordeolum (stye) – infected oil gland on the eyelid
- Conjunctivitis – bacterial or viral eye infection
- Blocked oil gland (chalazion) – can swell and sometimes become infected
- Blepharitis – chronic eyelid irritation
Common triggers:
Bacteria, touching eyes with unclean hands, poor eyelid hygiene, or contaminated makeup/towels.