A stye is caused by a bacterial infection in one of the tiny glands or hair follicles along your eyelid. The bacterium responsible is almost always Staphylococcus aureus, a common skin bacterium that normally lives on your face without causing problems. When it gets trapped inside a blocked gland or follicle, it multiplies, triggers inflammation, and produces that familiar red, painful bump near the edge of your eyelid.
How the Infection Starts
Your eyelids contain dozens of small oil-producing glands that help keep your tears from evaporating too quickly. Each eyelash also sits in its own follicle with its own tiny glands. When any of these openings get clogged with dead skin cells, dried oil, or debris, bacteria that were sitting harmlessly on the skin surface suddenly have a warm, sealed environment to grow in. The result is a localized infection: swelling, redness, and a tender lump that often comes to a visible white or yellow head.
External styes form at the base of an eyelash, where the follicle itself becomes infected. Internal styes develop deeper in the eyelid, inside one of the oil-producing glands. Internal styes tend to be more painful because the swelling presses against the eye, but both types share the same basic cause: bacteria plus a blocked opening.
Common Triggers and Risk Factors
Anything that increases the chance of clogging those gland openings or introducing bacteria raises your risk:
- Touching or rubbing your eyes with unwashed hands transfers bacteria directly to the eyelid margin.
- Old or shared eye makeup harbors bacteria and can physically block follicles. Mascara and eyeliner are the most common culprits.
- Sleeping in contact lenses changes the bacterial environment around your eyes and increases irritation along the lid.
- Incomplete makeup removal leaves residue that mixes with oil and seals off gland openings overnight.
These are the everyday triggers most people encounter. But for some people, styes keep coming back because of an underlying condition rather than a one-time habit.
Conditions That Cause Recurring Styes
If you get styes repeatedly, the issue is often chronic rather than incidental. Two conditions stand out.
Meibomian gland dysfunction is the most common culprit behind recurring styes. The meibomian glands are the oil glands embedded in your eyelids, and in the most typical form of this condition, they become chronically blocked so oil can’t flow out normally. That persistent blockage creates a near-constant setup for bacterial infection. According to Cleveland Clinic, chronic styes and repeated chalazions (a related but painless bump) are hallmark symptoms of meibomian gland dysfunction.
Blepharitis, a chronic inflammation of the eyelid margins, is closely linked to both meibomian gland dysfunction and recurrent styes. The two conditions often feed each other: inflamed eyelid margins produce more debris that clogs glands, and clogged glands worsen the inflammation. If the skin at the base of your lashes is frequently crusty, flaky, or red, blepharitis may be driving your styes.
Ocular rosacea is another less obvious cause. People with this condition commonly present with chronic red eyes, blepharitis, and frequent styes as early signs of ongoing inflammation. If you also have facial redness, flushing, or skin rosacea, ocular rosacea is worth investigating.
Stye vs. Chalazion
Not every eyelid bump is a stye. A chalazion looks similar but develops differently and feels different. A stye is an active bacterial infection. It’s very painful, appears right at the eyelid’s edge near an eyelash, and comes on quickly. A chalazion is a clogged oil gland without active infection. It forms farther back on the eyelid, grows more slowly, and is usually painless, at least initially. As a chalazion enlarges, the eyelid may become red and mildly tender, but the sharp pain of a stye is typically absent.
The distinction matters because their treatment paths differ. A stye that doesn’t resolve can sometimes turn into a chalazion once the acute infection fades but the blocked gland remains swollen.
How Long Styes Last
Most styes resolve on their own within one to two weeks. Many clear up within a week without any treatment at all. The single most effective thing you can do to speed that process is apply a warm compress: soak a clean washcloth in warm water, wring it out, and hold it gently against the closed eye for five minutes, several times a day. The heat softens the blocked oil and encourages the stye to drain naturally.
Resist the urge to squeeze or pop a stye. Forcing it open can spread the infection into surrounding tissue. Let it drain on its own or with the help of warm compresses.
If a stye hasn’t improved after one to two weeks of consistent warm compresses, or if it develops into a firm abscess, an eye doctor can perform a small incision and drainage. This is a minor in-office procedure reserved for stubborn cases.
Signs a Stye Needs Medical Attention
Styes rarely cause serious complications, but in uncommon cases the infection can spread beyond the bump into the soft tissue around the eye, a condition called periorbital cellulitis. Warning signs include swelling that spreads across the entire eyelid or to the surrounding skin, fever, or worsening redness that extends well beyond the original bump.
More serious is orbital cellulitis, where infection moves deeper behind the eye. This causes pain with eye movement, double vision, bulging of the eye, or decreased vision. These symptoms require urgent medical evaluation because the infection can progress quickly. If you notice any of these changes, especially pain when moving your eye or any change in vision, get care the same day.