A stye forms when one of the tiny oil glands in your eyelid gets blocked and then infected by bacteria, almost always Staphylococcus aureus. The blockage traps oil inside the gland, creating a warm, sealed environment where bacteria multiply quickly. Within a few days, your immune system sends white blood cells to fight the infection, and the resulting battle produces a small, painful abscess: the red, swollen bump you recognize as a stye.
The Step-by-Step Process
Your eyelids contain dozens of oil-producing glands. Their job is to release a thin layer of oil onto the surface of your eye every time you blink, which keeps your tears from evaporating too fast. When the duct of one of these glands gets clogged by dead skin cells, dried oil, debris, or makeup residue, the oil backs up inside the gland with nowhere to go.
Staph bacteria, which live harmlessly on most people’s skin, seize the opportunity. The trapped oil is an ideal growth medium. As bacteria colonize the blocked gland, your immune system responds with a flood of infection-fighting cells. That inflammatory response is what causes the redness, swelling, warmth, and tenderness. The gland fills with pus and forms a localized abscess, which is the visible bump on your eyelid. Most styes come to a head and either drain on their own or resolve with basic home care within one to two weeks.
External vs. Internal Styes
Not all styes form in the same place, and the location depends on which gland is affected.
An external stye develops in one of the small oil glands (called glands of Zeis) that open directly into your eyelash follicles. Because the infection sits right at the base of a lash, it looks like a pimple on the outer edge of your eyelid. This is the most common type and the one most people picture when they hear the word “stye.”
An internal stye forms deeper in the eyelid, in one of the larger oil glands (meibomian glands) embedded in the eyelid tissue itself. These tend to point inward rather than outward, sometimes showing as a yellowish spot on the inner surface of the lid when you pull it back. Internal styes can feel more painful because they press against the eyeball, and they’re more likely to linger or develop into a firm, painless lump called a chalazion if the inflammation doesn’t fully clear.
Styes vs. Chalazia
A chalazion looks similar to a stye but behaves differently. While a stye is an acute bacterial infection that comes on fast, hurts, and often produces pus, a chalazion is a slower inflammatory reaction to trapped oil. It typically shows up as a firm, round nodule that’s not particularly painful and doesn’t have the angry redness of an active infection. Chalazia develop more gradually over weeks, whereas styes peak within days.
The distinction matters because their treatment differs. A stye usually resolves with warm compresses and time. A chalazion that doesn’t shrink on its own may need a minor in-office procedure to drain it. Sometimes a stye that doesn’t fully resolve transitions into a chalazion as the acute infection fades but the blocked, inflamed gland tissue remains.
What Increases Your Risk
Some people get styes once and never again. Others deal with them repeatedly. The difference often comes down to underlying conditions that keep the eyelid glands chronically irritated or dysfunctional.
Blepharitis, a condition where the eyelid margins stay persistently inflamed, is one of the strongest risk factors. The ongoing inflammation disrupts normal oil flow and makes blockages more likely. Ocular rosacea, a form of rosacea that affects the eyes, creates a similar problem. People with ocular rosacea commonly present with chronic red eyes, inflamed eyelid margins, and frequent styes as part of the disease’s pattern. The condition involves overactive inflammatory signaling and can also encourage the overgrowth of tiny mites (Demodex) that live on eyelash follicles, further destabilizing the gland environment.
Everyday habits play a role too. A large cross-sectional study of eye makeup users found that 16.4% reported recurrent styes. The risk factors were predictable but striking in how common they are: only about half of users always washed their hands before applying eye makeup, roughly 60% shared makeup with family or others, and only about 10% cleaned their applicators every time they used them. Using tester products at cosmetics counters nearly doubled the odds of eye-related problems. Old makeup is another culprit. Over half of the women surveyed kept products until the bottle was empty rather than discarding them at expiration, giving bacteria more time to colonize the product.
Contact lens wearers face additional risk if they handle lenses without clean hands or wear them longer than recommended. Touching or rubbing your eyes frequently can also introduce bacteria to the lid margin.
What a Stye Feels Like
The first sign is usually a tender, slightly swollen spot on the eyelid that feels like a bruise when you blink. Over the next day or two, the area becomes visibly red and puffy. A small bump appears, sometimes with a white or yellowish center where pus is collecting. Your eye may water more than usual, and you might feel a gritty sensation, as though something is stuck under the lid.
The discomfort typically peaks around days two to three. After that, most styes either drain on their own (you’ll notice the bump shrinking and some discharge on your lashes) or gradually reabsorb. The entire process from first twinge to full resolution usually takes one to two weeks.
Helping a Stye Heal
Warm compresses are the most effective home treatment. Soaking a clean washcloth in warm water and holding it against the closed eyelid for 10 to 15 minutes, several times a day, softens the clogged oil and encourages the stye to drain naturally. Rewarm the cloth as it cools. Gentle massage of the area after a compress can help move things along.
Resist the urge to squeeze or pop a stye. Forcing it open can push the infection deeper into the eyelid tissue or spread bacteria to surrounding glands. Let it drain on its own. Avoid wearing eye makeup or contact lenses while a stye is active, since both can reintroduce bacteria and slow healing.
If the pain and swelling haven’t started improving after about 48 hours of consistent warm compresses, or if the swelling gets worse after the first two to three days rather than better, it’s worth having it evaluated. Persistent styes sometimes need a small drainage procedure or a short course of treatment to clear the infection.
When a Stye Becomes Something More Serious
Styes rarely cause serious complications, but the eyelid sits in a region with rich blood supply and close proximity to the eye socket and sinuses. In uncommon cases, a stye’s infection can spread to the surrounding soft tissue of the eyelid, causing periorbital cellulitis. This shows up as widespread redness and swelling across the entire eyelid, not just a localized bump. It’s most common in young children.
The key warning signs that an infection has moved beyond a simple stye include swelling that spreads well beyond the bump itself, fever, eye pain that worsens with movement, double vision, a bulging eye, or any change in how well you can see. These symptoms suggest the infection may have penetrated deeper into the tissue around or behind the eye, which requires prompt medical attention. A simple stye should never affect your vision or make it painful to move your eye. If it does, something else is going on.