Styes are caused by an infection of the oil glands in the eyelids, most commonly by the bacteria Staphylococcus aureus. This bacterium normally lives on the skin, nose, and eyelashes but can cause infection when it blocks the oil glands around the eyelashes or within the eyelid, leading to a painful, red bump that resembles a pimple. Factors such as poor hygiene, rubbing the eyes with unclean hands, improper contact lens hygiene, using old or contaminated makeup, certain skin conditions like rosacea and blepharitis, and weakened immune systems (e.g., due to diabetes) can increase the risk of developing a stye.
In summary:
- The main cause is bacterial infection, particularly Staphylococcus aureus.
- The infection occurs when oil glands in the eyelids become blocked and infected.
- Risk factors include poor hygiene, contaminated eye products, skin disorders, and immune system issues.
- Styes can occur on the outer or inner part of the eyelid and cause redness, swelling, tenderness, and sometimes discharge.
This explains what causes styes and why they form.
