An eye stye is usually caused by a small bacterial infection in an oil gland at the edge of your eyelid, most often from the common skin bacterium Staphylococcus aureus.

What a stye actually is

  • A stye (also called a hordeolum) is a red, tender bump on the eyelid, like a pimple or boil.
  • It forms when an eyelid oil gland or eyelash follicle gets clogged and then infected.
  • It can be external (near the lash line) or internal (on the inside of the lid, in a meibomian gland).

Main causes: what’s happening

The core cause is infection of an oil gland by bacteria, usually Staphylococcus aureus. This bacteria normally lives harmlessly on the skin, but if it gets trapped in a blocked gland, it can trigger an infection and swelling.

Common triggers for that blockage and infection include:

  • Poor eyelid or hand hygiene (rubbing eyes with unwashed hands).
  • Old, expired, or shared eye makeup.
  • Leaving mascara or eyeliner on overnight.
  • Improper contact lens hygiene (not cleaning lenses or hands properly).
  • Oil, sweat, or makeup buildup around the lashes that clogs glands.

Who gets styes more often (risk factors)

Certain conditions and habits make styes more likely:

  • Chronic eyelid inflammation (blepharitis).
  • Skin conditions like rosacea or seborrheic dermatitis.
  • Diabetes or a weakened immune system.
  • History of frequent styes in the past.
  • Not regularly washing the face and eyelids; not removing eye makeup fully.

Some sources also note that poor sleep, stress, and poor nutrition may indirectly raise risk by affecting immunity and eyelid health, but they are not direct causes like bacteria and blocked glands.

Myths vs reality

  • “Styes are caused by stress” → Stress does not directly cause a stye, but it can weaken immunity and make infections slightly more likely.
  • “A stye means you’re dirty” → Not necessarily; hygiene plays a role, but even people with good hygiene can get styes because the bacteria live normally on skin and lashes.

Quick Scoop: how to reduce your risk

  • Wash your hands before touching your eyes or contact lenses.
  • Remove all eye makeup every night and avoid old or shared products.
  • Gently clean eyelids (for example with a warm, damp cloth) if you tend to get crusting or irritation.
  • If you have rosacea, blepharitis, or frequent styes, ask an eye doctor about a regular lid hygiene routine.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.