You get a sty when bacteria infect one of the small glands along your eyelid margin. The culprit is almost always Staphylococcus aureus, a common bacterium that lives on your skin and finds its way into a blocked or irritated gland. From there, the gland swells into a painful, red bump that typically lasts one to two weeks before draining on its own.
Understanding the specific ways bacteria reach your eyelids helps explain why some people get sties once and never again, while others deal with them repeatedly.
What Happens Inside Your Eyelid
Your eyelids contain dozens of tiny glands that produce oils to keep your eyes lubricated. When one of these glands gets clogged, its oily secretions thicken and stagnate. That stagnant fluid becomes a perfect environment for staph bacteria to multiply, triggering an infection that swells into a sty.
Most sties are external, forming right at the base of an eyelash where it meets the glands along the lid’s edge. A small yellowish pustule develops at the eyelash root, and within two to four days it typically ruptures, releases pus, and starts healing. Internal sties are less common and form deeper in the eyelid, inside oil-producing glands called meibomian glands. These tend to be more painful and take longer to resolve because they don’t drain as easily.
Common Ways Bacteria Reach Your Eyes
The bacteria that cause sties are already on your skin. The real question is what gives them access to a vulnerable gland. Several everyday habits create that opportunity:
- Touching your eyes with unwashed hands. This is the most straightforward route. Rubbing your eyes transfers staph bacteria directly to the eyelid margin.
- Sleeping in makeup. Eye makeup that isn’t fully removed at night can block gland openings and introduce bacteria. Mascara, eyeliner, and eyeshadow sit right against the glands most susceptible to infection.
- Using expired or shared cosmetics. Old creams, powders, and liners harbor bacteria. Sharing makeup, brushes, towels, or even pillows can spread bacteria between people.
- Wearing contact lenses with poor hygiene. Handling lenses without clean hands or using old solution introduces bacteria to the eye area.
None of these guarantee a sty. But each one increases the chance that bacteria will meet a clogged gland at the right moment.
Why Some People Get Sties Repeatedly
If you keep getting sties, the underlying cause is usually a chronic eyelid condition rather than a single hygiene lapse. Blepharitis, a persistent low-grade inflammation of the eyelid margins, is the most common link. It causes the oil glands to thicken and clog more easily, setting the stage for repeated infections.
Ocular rosacea is another contributor. People with this condition develop ongoing meibomian gland dysfunction, where the oil glands in the eyelids don’t work properly. The hallmarks are chronic blepharitis in both eyes, burning, and a gritty foreign-body sensation. Some patients develop recurrent lumps on their eyelids as a direct result of this gland dysfunction. Left untreated over time, repeated episodes can even lead to corneal scarring.
Recurrence is common when daily eyelid hygiene isn’t maintained between episodes. If you’ve had more than one sty, the pattern is unlikely to stop without a consistent prevention routine.
How a Sty Differs From a Chalazion
A sty and a chalazion can look similar at first, but they behave differently. A sty is an active infection. It’s painful from the start, localizes to the eyelid margin, and usually comes to a head within a few days. A chalazion is a blockage without infection. It starts as a small, nontender nodule deeper in the eyelid body, and it develops more gradually.
The key distinction is pain. A sty hurts, especially when touched, and the area around it turns red and swollen. A chalazion may cause mild discomfort from its size, but it isn’t typically painful. Sometimes a sty that doesn’t fully drain can turn into a chalazion as the remaining blocked material hardens into a painless lump.
What to Do When You Have One
Warm compresses are the primary home treatment. Holding a clean, warm cloth against the affected eyelid for 10 to 15 minutes, several times a day, helps soften the blocked material and encourages the sty to drain naturally. Most sties resolve within one to two weeks with this approach alone.
What you shouldn’t do matters just as much. Squeezing or popping a sty forces bacteria deeper into the tissue and can spread the infection. Avoid wearing contact lenses or eye makeup on the affected eye until it heals.
If pain and swelling are still increasing after two to three days of warm compresses, or if they haven’t started improving within 48 hours, it’s worth having an eye doctor take a look. A sty that won’t resolve on its own may need to be drained professionally or treated with medication.
When a Sty Becomes Something More Serious
In rare cases, the infection from a sty can spread into the surrounding skin, causing a condition called preseptal cellulitis. The swelling expands beyond the bump itself, and the entire eyelid or the skin around the eye becomes red, puffy, and tender to touch. This doesn’t typically cause fever or eye pain, which helps distinguish it from deeper infections.
The more dangerous scenario is when infection spreads behind the eye into the orbit. Signs that this is happening include fever, eye pain, vision changes, and the eye itself starting to bulge forward. This requires emergency care, particularly in children, who are more vulnerable to this progression.
Preventing Sties
Daily eyelid hygiene is the single most effective prevention strategy. Washing the eyelid margins with mild soap and warm water removes excess oils before they can clog glands. If you’re prone to sties, commercial eyelid scrubs can help keep the gland openings clear, and your eye doctor may recommend a specific product based on what’s causing your recurrences.
Beyond that, the basics matter: wash your hands thoroughly before touching the area around your eyes, remove all eye makeup before bed using a gentle cleanser, replace mascara and eyeliner regularly, and never share eye cosmetics or tools. Clean your contact lenses properly and replace them on schedule. These habits won’t eliminate every risk, but they remove the most common pathways bacteria use to reach your eyelid glands.