A stye forms when bacteria infect one of the tiny oil glands along your eyelid margin. The culprit is almost always Staphylococcus aureus, a common bacterium that already lives on your skin and eyelashes. When it gets trapped inside a gland or hair follicle, the resulting infection creates a painful, red bump that looks like a small pimple on the edge of your eyelid.
Most styes resolve on their own within one to two weeks, but understanding how they develop in the first place can help you avoid repeat episodes.
What Happens Inside Your Eyelid
Your eyelids contain dozens of small glands that produce oils to keep your eyes lubricated. Two types of glands matter here. The glands of Zeis sit right at the base of each eyelash and release oil into the hair follicle. Deeper inside the eyelid, the Meibomian glands line the inner surface and secrete oil through tiny openings along the lid margin. When either type gets clogged or contaminated with bacteria, infection sets in.
An external stye, the more common type, starts at the root of an eyelash where the glands of Zeis are located. You’ll see redness and swelling concentrated around one lash, often with a visible yellowish head as the infection progresses. An internal stye develops when a Meibomian gland becomes infected deeper within the eyelid. These tend to point inward, producing a yellow spot on the inner surface of the lid. Internal styes can be harder to see but often feel more uncomfortable because of their position.
Common Causes and Triggers
Bacteria on your eyelashes are normal and usually harmless. A stye develops when something gives those bacteria an opportunity to multiply inside a gland. Several everyday habits and conditions create that opportunity.
Touching your eyes with unwashed hands is one of the most straightforward ways to introduce extra bacteria to your eyelids. Rubbing your eyes, adjusting contact lenses, or even wiping away tears with dirty fingers can push bacteria into a gland opening.
Old or shared eye makeup is a major contributor that many people overlook. Eyelashes naturally carry bacteria, and the moment a mascara wand or eyeliner brush touches your lashes, it picks up those organisms and deposits them back into the product container. Over time, bacterial levels in the cosmetic build up, increasing the infection risk with every application. Experts suggest replacing mascara and eyeliner every three to four months to limit this buildup. Storing cosmetics above 85°F (such as in a hot car) weakens the preservatives that keep bacteria in check, making the products riskier to use even before they technically expire.
Sleeping in makeup keeps oil glands blocked for hours. Overnight, the combination of old cosmetics, dead skin cells, and natural oils creates an ideal environment for bacteria to colonize a clogged gland.
Contact lens habits also play a role. Handling lenses without washing your hands, wearing them longer than recommended, or reusing solution all raise the odds of transferring bacteria to your eyelid.
Chronic Conditions That Raise Your Risk
Some people get styes repeatedly, and the reason often traces back to an underlying eyelid condition. Blepharitis, a chronic inflammation of the eyelid margins, is one of the most common links. When the eyelid edges stay inflamed, oil glands don’t drain properly, and bacteria find it easier to take hold. Blepharitis itself has several triggers, including the skin condition rosacea, which changes the skin’s oil production and increases inflammation around the face and eyes.
People with rosacea have a higher baseline risk for eyelid problems in general. The same inflammatory process that causes facial redness can affect the Meibomian glands, leading to chronic blockages that become styes or a related bump called a chalazion.
Stye vs. Chalazion
A chalazion can look similar to a stye but develops differently. While a stye is an active bacterial infection that’s red, painful, and tender from the start, a chalazion forms when an oil gland clogs and the trapped oil causes a slow, painless swelling. Chalazia typically aren’t infected, just blocked. They tend to develop further from the eyelid edge and grow more gradually.
The distinction matters because chalazia sometimes develop from styes that don’t fully drain. If a stye loses its tenderness but leaves behind a firm, painless lump, it has likely transitioned into a chalazion.
How a Stye Feels and Progresses
The first sign is usually tenderness and redness at one spot on the eyelid. Within a day or two, that spot swells into a defined bump. Your eye may feel sore, scratchy, or watery. Some people notice their entire eyelid swelling, especially with internal styes. As the infection matures, a small yellowish point often appears at the center of the bump, similar to a pimple coming to a head.
Most styes rupture and drain on their own within one to two weeks. Applying a clean, warm compress for 10 to 15 minutes several times a day speeds this process by softening the clogged oil and encouraging the gland to open. Resist the urge to squeeze or pop a stye, which can spread the infection deeper into the eyelid tissue.
Signs That Need Medical Attention
Most styes are minor and self-limiting, but certain symptoms suggest the infection is worsening or something else is going on. You should see an eye doctor if:
- Pain and swelling increase after the first two to three days instead of improving
- Your eyelid swells shut
- Pus or blood leaks from the bump
- Blisters form on your eyelid
- Your eyelids feel hot to the touch
- Your vision changes
- Styes keep coming back
If home care with warm compresses hasn’t produced any improvement after 48 hours, that’s a reasonable point to seek professional evaluation.
Preventing Styes
Because styes are caused by bacteria that already live on your skin, prevention is really about keeping those bacteria from getting trapped in a gland. Wash your hands before touching your face or handling contact lenses. Remove all eye makeup before bed with a gentle cleanser. Replace mascara and eyeliner every three to four months, and never share eye cosmetics with others. Don’t spit into eye products to moisten them, as mouth bacteria can contaminate the product and later cause infection.
If you have blepharitis or tend to get styes repeatedly, a daily eyelid hygiene routine can make a real difference. Gently cleaning the lid margins with a warm washcloth or commercially available lid wipes helps keep the oil glands clear and reduces the bacterial load along the lash line.