Styes are caused by a bacterial infection in one of the tiny oil glands along your eyelid. The culprit is almost always Staphylococcus aureus, a common bacterium that lives on your skin. When an oil gland gets blocked, secretions build up and stagnate, creating the perfect environment for bacteria to multiply. The result is that familiar red, tender bump that looks like a pimple on your eyelid.
How a Stye Actually Forms
Your eyelids contain dozens of small glands that produce oils to keep your eyes lubricated. When one of these glands becomes clogged, the oil inside thickens and stops flowing. Bacteria that normally live harmlessly on your skin surface move into the stagnant gland, triggering an infection. Your immune system responds with inflammation, and within a day or two, a painful, swollen bump appears.
There are two types. External styes form in the oil or sweat glands right at the base of your eyelashes (called the glands of Zeis or Moll). These are the most common kind and look like a pimple sitting on the edge of your lid. Internal styes form deeper inside the eyelid, in the larger meibomian glands that line the inner surface. Internal styes tend to be more painful because they press against the eye itself. When they drain, they release material onto the inner surface of the eyelid rather than the outer skin.
Risk Factors That Make Styes More Likely
Some people get styes once and never again. Others deal with them repeatedly. The difference often comes down to underlying conditions that keep the oil glands irritated or chronically blocked.
Blepharitis, a condition where the eyelid margins stay inflamed, is the single biggest risk factor. It creates ongoing congestion in the oil glands, which means bacteria always have a foothold. People with skin conditions like rosacea, acne, or seborrheic dermatitis face a similar problem: their oil glands tend to produce thicker, stickier secretions that clog more easily. Hormonal changes, diabetes, and high cholesterol also increase your risk by altering the composition of the oils your glands produce.
If you keep getting styes, one of these underlying conditions is likely the reason. Treating the stye alone won’t break the cycle.
Makeup, Contacts, and Hygiene Triggers
Beyond medical conditions, everyday habits play a significant role. Eye makeup is a common trigger because applicators touch both the product and your eyelid repeatedly, transferring bacteria back and forth. Old makeup compounds the problem. Mascara and liquid eyeliner should be replaced every four months, while solid eye pencils last up to a year. Beyond that, the product itself becomes a breeding ground for bacteria. Reusing contaminated makeup can cause recurring styes even though styes themselves aren’t contagious from person to person.
Contact lens wearers face added risk if they skip proper disinfection, wear lenses past their recommended lifespan, or handle lenses with unwashed hands. Touching or rubbing your eyes throughout the day also introduces bacteria directly to your eyelid glands.
How Long Styes Last
Most styes resolve on their own within one to two weeks. The standard home treatment is a warm compress: a clean washcloth soaked in warm water, held gently against the affected eye for five minutes, several times a day. The warmth helps liquefy the hardened oil inside the blocked gland, encouraging it to drain naturally.
You should notice improvement within 48 hours of starting warm compresses. If pain and swelling are still increasing after two to three days, that’s a sign the infection isn’t resolving on its own. In rare cases where a stye persists for weeks despite home care, or where an abscess forms, a doctor can drain it through a small procedure in a sterile setting. This is uncommon for typical styes but more relevant for internal ones that don’t have an easy path to drain.
Stye vs. Chalazion
A chalazion looks a lot like a stye but behaves differently. Styes are acute infections: they come on fast, hurt when touched, and make blinking painful. A chalazion is a chronic, usually painless lump that forms when a blocked gland becomes inflamed without an active bacterial infection. Chalazia develop more slowly and can linger for one to two months. Many chalazia start as styes that didn’t fully resolve. If a chalazion persists beyond a couple of months, surgical drainage may be needed.
When a Stye Becomes Serious
Styes are almost always harmless, but in rare cases the infection can spread beyond the gland into the surrounding eyelid tissue. This is called preseptal (or periorbital) cellulitis. The hallmark is swelling and redness that extends well beyond the bump itself, spreading across the eyelid or around the eye socket, often accompanied by fever and increasing pain.
If the infection pushes deeper, past the thin membrane that separates your eyelid from your eye socket, it becomes orbital cellulitis, a genuinely dangerous condition. Signs include the eye bulging forward, pain with eye movement, vision changes, and fever. This requires emergency care. In children especially, fever combined with pain and swelling around the entire eye socket warrants an immediate trip to the emergency room.
For the vast majority of styes, though, warm compresses and clean hands are all you need. Keeping your eyelids clean, replacing old makeup on schedule, and managing any underlying skin conditions are the most effective ways to prevent them from coming back.