A stye forms when bacteria infect one of the tiny oil or sweat glands in your eyelid. Your eyelids contain dozens of these glands, and when one gets blocked, bacteria already living on your skin can multiply inside, triggering the painful, red bump most people recognize as a stye. The whole process typically plays out over one to two weeks before resolving on its own.
What Happens Inside Your Eyelid
Your eyelids have two types of oil-producing glands and one type of sweat gland, all clustered near your lash line. Small oil glands sit right at the base of each eyelash follicle, and modified sweat glands sit nearby. Deeper inside the eyelid, a row of larger oil glands runs through the firm tissue (called the tarsal plate) that gives your eyelid its shape. These deeper glands produce the oily outer layer of your tear film, the coating that keeps your eyes from drying out between blinks.
A stye begins when one of these glands gets clogged. Dead skin cells, dried oil, or debris can block the gland’s opening. Bacteria, almost always Staphylococcus aureus (a species that normally lives on your skin in small numbers), slip into the blocked gland and begin multiplying. Your immune system responds with inflammation: blood flow increases, white blood cells rush to the area, and pus collects. That’s the tender, swollen bump you feel.
External vs. Internal Styes
Not all styes look or feel the same, because the gland involved determines where the infection sits.
An external stye is the more common type. It develops when the small oil or sweat glands at the base of an eyelash become infected. Because these glands are right at the lid margin, you’ll usually see a visible white or yellow pustule forming on the outer edge of the eyelid, near the lash line. These tend to be painful but well-defined.
An internal stye affects the larger oil glands embedded deeper within the eyelid. Because the infection is farther from the surface, internal styes look more like a generalized swelling of the lid rather than a pinpoint bump. They can feel like a deep ache or pressure, and the redness may spread across more of the eyelid.
Why Some People Get Styes More Often
Several factors raise the odds of a gland becoming blocked and infected. Chronic eyelid inflammation (blepharitis) is one of the biggest contributors. When the lid margins stay irritated over time, the glands are more likely to clog, creating an entry point for bacteria. Skin conditions like rosacea and seborrheic dermatitis are closely linked. One study found that people who had styes during childhood were nearly four times more likely to develop rosacea as adults compared to controls (5.5% vs. 1.5%), suggesting the two conditions share underlying inflammatory pathways.
Everyday habits matter too. Touching or rubbing your eyes transfers bacteria from your hands directly to your eyelids. Old eye makeup is another common culprit. Your eyelashes naturally carry bacteria, so the moment a mascara wand or eyeliner brush touches them, the product is contaminated. Over time, bacteria build up inside the cosmetics container. Experts recommend replacing mascara and eyeliner every three to four months to reduce infection risk. Sleeping in makeup gives bacteria extra hours in contact with gland openings.
Contact lens wearers face elevated risk if they handle lenses without washing their hands, and people under significant stress or sleep deprivation may be more susceptible because their immune response is less efficient at keeping normal skin bacteria in check.
How a Stye Progresses
Most styes follow a predictable pattern. In the first day or two, you’ll notice tenderness, slight swelling, and redness at a specific spot on the lid. Over the next few days, the bump grows and may develop a visible head of pus (for external styes). Blinking can feel uncomfortable, and the eye may water more than usual.
By the end of the first week, many styes begin to drain on their own. The bump softens, the pus finds a way out, and the swelling starts to recede. Full resolution typically takes one to two weeks. Some styes never form a visible head and simply reabsorb.
The Difference Between a Stye and a Chalazion
People often confuse styes with chalazia, and the two can look similar at first. The key distinction is that a stye is an active bacterial infection, so it’s red, warm, and painful. A chalazion is a blocked gland that has become chronically inflamed but isn’t actively infected. It usually presents as a firm, painless lump in the lid that grows slowly over weeks. A stye that doesn’t fully drain can sometimes turn into a chalazion as the body walls off the remaining material.
Helping a Stye Heal
The most effective home treatment is a warm compress. Soak a clean washcloth in warm water, wring it out, and hold it gently against the closed eyelid for about five minutes. Repeat several times a day. The warmth loosens the clogged oil, encourages drainage, and increases blood flow to the area so your immune system can clear the infection faster.
Resist the urge to squeeze or pop a stye. Forcing it open can push bacteria deeper into the tissue or spread the infection to neighboring glands. Keep the area clean, avoid wearing eye makeup until the stye resolves, and wash your hands before touching your face. If you wear contact lenses, switch to glasses until the bump is gone.
Most styes resolve without any medical intervention. Styes that persist beyond two weeks, grow unusually large, or cause significant swelling across the entire lid sometimes need to be drained by a doctor in a quick in-office procedure.
When a Stye Becomes Something More Serious
In rare cases, the infection can spread beyond the gland into the surrounding soft tissue of the eyelid, a condition called periorbital cellulitis. Signs that a stye has progressed include worsening redness and swelling that extends well beyond the bump, fever, or the eyelid becoming so swollen it’s difficult to open. If the infection pushes deeper into the eye socket, it can cause eye pain with movement, double vision, the eye appearing to bulge forward, or changes in vision. These symptoms require prompt medical attention because orbital infections can threaten eyesight.
Preventing Recurrence
If you get styes repeatedly, the focus shifts to keeping your eyelid glands clear and reducing the bacterial load on your lids. A nightly routine of gently cleaning your lid margins with a warm washcloth or diluted baby shampoo can make a real difference. Replace eye cosmetics every three to four months, never share makeup, and clean makeup brushes regularly. Washing your hands before inserting contact lenses and before touching your eyes reduces bacterial transfer.
For people with blepharitis or rosacea, treating the underlying condition is often the most effective way to break the cycle. Keeping lid inflammation under control means the glands stay open and functional, leaving bacteria fewer opportunities to take hold.