A stye is caused by a bacterial infection in one of the small glands along your eyelid. The bacterium responsible in most cases is Staphylococcus aureus, a common germ that already lives on your skin. When it gets trapped inside a blocked gland or hair follicle on the eyelid, it multiplies, and the result is a painful, red bump that looks a bit like a pimple.
How the Infection Starts
Your eyelids contain dozens of tiny oil-producing glands. Their job is to coat your tears with a thin layer of oil so they don’t evaporate too quickly. Each eyelash also sits in its own follicle with small glands attached. When any of these glands gets clogged with dead skin cells, dried oil, or debris, bacteria that normally sit harmlessly on the skin surface can become trapped inside. Cut off from air and surrounded by nutrients, the bacteria multiply rapidly. Your immune system responds with inflammation, and within a day or two you have a swollen, tender lump.
External vs. Internal Styes
Not all styes form in the same spot. An external stye develops right at the base of an eyelash, in the small oil or sweat glands attached to the follicle. These are the most common type and tend to look like a whitehead sitting on the edge of your lid.
An internal stye forms deeper inside the eyelid, in the larger oil glands embedded in the lid’s firm inner plate. Because they’re buried under more tissue, internal styes can be harder to see but often cause more widespread swelling and discomfort. They also take longer to resolve on their own.
Common Triggers and Risk Factors
Staph bacteria are everywhere, so the real question is what gives them the opportunity to cause trouble. Several everyday habits and conditions raise your risk.
- Sleeping in eye makeup. Cosmetics left on overnight can block gland openings and fuel bacterial growth on the lid margin. Applicators also transfer bacteria back and forth between your eyes and the product each time you use them.
- Using expired makeup. Old mascara and liquid eyeliner become breeding grounds for bacteria. Replace mascara and liquid liner every four months. Solid eye pencils can last up to a year.
- Touching your eyes with unwashed hands. This is one of the simplest ways to introduce staph bacteria directly to your eyelid.
- Improper contact lens care. Failing to disinfect lenses, reusing old solution, or wearing contacts past their recommended lifespan all increase the chance of transferring bacteria to the eye area.
- Blepharitis. This is chronic low-grade inflammation of the eyelid margins. People with blepharitis tend to have more clogged glands and more bacteria along the lash line, making recurrent styes common.
- Rosacea. The skin condition can affect the eyelids and contribute to gland dysfunction, creating conditions favorable for styes.
Stye vs. Chalazion
A stye and a chalazion can look similar, but they feel different and have different causes. A stye is an active infection. It’s red, swollen, and tender to touch, and it often comes on quickly.
A chalazion is not an infection. It forms when a blocked oil gland triggers an inflammatory reaction to the trapped oil itself. The result is a firm, painless nodule in the eyelid that develops more slowly and can linger for weeks or months. Sometimes a stye that doesn’t fully drain will harden into a chalazion over time. If you have a bump on your eyelid that isn’t painful, it’s more likely a chalazion than a stye.
What a Stye Feels Like
Most styes announce themselves before you can see them. You’ll notice a gritty, sore sensation along the eyelid, almost like something is stuck in your eye. Within a day, the area swells and a distinct bump appears. The skin around it turns red. Your eye may water more than usual, and blinking can feel uncomfortable. Some people notice their whole eyelid puffs up even though the stye itself is small. After a few days, many styes develop a visible yellow or white point at the surface, similar to a pimple coming to a head.
How Long a Stye Lasts
Most styes drain on their own within one to three weeks without any medical treatment. The bump gradually softens, comes to a point, and releases a small amount of pus before healing. Applying a warm compress for about five minutes several times a day can speed this process. Soak a clean washcloth in warm water, wring it out, and hold it gently against the closed eye. The warmth helps liquefy the hardened oil blocking the gland, encouraging drainage.
Resist the urge to squeeze or pop the stye. Forcing it open can spread the infection to surrounding tissue and make things significantly worse. If a stye hasn’t started improving after a week of warm compresses, or if it keeps growing, a doctor can prescribe antibiotic drops or ointment. In rare cases involving severe infection, oral antibiotics may be needed. Some stubborn styes require a small in-office drainage procedure.
When a Stye Becomes Serious
The vast majority of styes are annoying but harmless. Rarely, the infection can spread beyond the gland into the surrounding skin of the eyelid, a condition called preseptal cellulitis. Signs that this is happening include a fever, pain and swelling that extends well beyond the original bump, and redness spreading across the eyelid or toward the cheek. If the infection pushes deeper into the eye socket, it can cause eye pain, vision changes, or bulging of the eye. These symptoms need emergency medical attention, particularly in children, because orbital cellulitis can threaten vision and overall health if left untreated.
Preventing Recurrent Styes
If you’ve had one stye, your odds of getting another are higher, especially if the underlying trigger hasn’t changed. A few habits make a noticeable difference. Wash your hands before touching your face or handling contact lenses. Remove all eye makeup before bed every night. Replace mascara and liquid liner on schedule rather than using them until they run out. If you wear contacts, follow the recommended replacement and disinfection routine strictly, and switch to glasses while you have an active stye.
For people with chronic eyelid inflammation, a daily lid-hygiene routine helps. This means gently cleaning the base of the lashes each morning with a warm washcloth or commercially available lid wipes to keep gland openings clear of debris. Over time, consistent lid care reduces the bacterial load along the lash line and makes styes far less frequent.