Styes form when bacteria, almost always Staphylococcus, infect one of the small oil or sweat glands along your eyelid margin. The infection causes a blocked gland to swell into a tender, red bump that typically develops over a few days. Most of the time, the bacteria responsible are already living on your skin or inside your nose, and they reach your eyelid through everyday habits like rubbing your eyes.
What Happens Inside the Eyelid
Your eyelids contain dozens of tiny glands that produce oils and sweat to keep your eyes lubricated. When one of these glands gets clogged with dead skin cells, dried oil, or debris, bacteria that normally live harmlessly on your skin can multiply inside the blocked gland. Your immune system responds with inflammation, and the result is that painful, pimple-like bump.
There are two types, depending on which glands are involved. An external stye forms near the base of an eyelash, in the small oil or sweat glands right at the lid margin. These are the ones you can usually see and feel on the outside of your eyelid. An internal stye develops deeper, in the larger oil-producing glands embedded in the firm tissue of the eyelid itself. Internal styes tend to be more painful because they press against the eye, and they sometimes point inward rather than outward.
The Most Common Ways Bacteria Reach Your Eye
Staphylococcus bacteria are extremely common. Many people carry them in their nose without any problems. But if you touch your nose and then rub your eye, you can transfer bacteria directly to the glands along your lash line. That single habit accounts for a large share of stye cases.
Other common routes include:
- Old eye makeup. Mascara and liquid eyeliner are considered safe for about three months. After that, bacterial growth in the product increases significantly. Pencil eyeliners last longer, up to a year, because they’re less hospitable to bacteria.
- Sleeping in makeup. Leaving eye makeup on overnight gives bacteria hours to work into clogged glands.
- Dirty contact lenses or cases. Handling lenses without washing your hands first is one of the easiest ways to introduce bacteria to your eyelid.
- Shared towels or pillowcases. Styes are rarely contagious, but the bacteria that cause them can transfer through fabrics that touch the face. If someone in your household has a stye, using separate towels and pillowcases is a reasonable precaution.
Who Gets Styes More Often
Some people get a stye once and never again. Others deal with them repeatedly, and that often points to an underlying condition that keeps the eyelid glands irritated or partially blocked.
Blepharitis, a chronic low-grade inflammation of the eyelid margins, is one of the most common risk factors. It causes flaky, irritated lids that are prone to gland blockages. Ocular rosacea is another. It’s closely tied to dysfunction of the oil glands in the eyelid, and styes are listed among its most frequent complications. People with very oily skin, those who have had styes before, and anyone dealing with hormonal changes that affect oil production also tend to be more susceptible.
Stress and sleep deprivation don’t directly cause styes, but they suppress immune function enough that your body may be slower to fight off a minor bacterial invasion at the eyelid margin.
What a Stye Feels and Looks Like
Most styes announce themselves with tenderness or a gritty sensation at one spot on the eyelid before any bump is visible. Over the next day or two, the area reddens and swells into a firm, painful lump roughly the size of a pea. The eyelid around it may puff up, and your eye might water more than usual. Some styes develop a visible white or yellow head, similar to a pimple, as pus collects near the surface.
The whole process from first twinge to full bump typically takes just a few days. Most styes drain on their own within a week or two without any treatment beyond warm compresses.
Treating a Stye at Home
The single 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 this several times a day. The warmth loosens the clogged oil inside the gland and encourages the stye to drain naturally. You may need to re-wet the cloth partway through to keep it warm.
Resist the urge to squeeze or pop the stye. Forcing it open can spread the infection deeper into the eyelid or into surrounding tissue. If the stye has a visible head, the warm compress will usually bring it to a point where it drains on its own. Keep the area clean, avoid wearing eye makeup until it heals, and wash your hands before touching anything near your eyes.
When a Stye Signals Something More Serious
A straightforward stye is a small, localized bump. If swelling spreads across the entire eyelid or around the eye socket, the infection may have moved beyond the gland into the surrounding skin, a condition called cellulitis. The key warning signs that separate a simple stye from a more serious infection are fever, swelling that extends well beyond the bump, pain with eye movement, changes in vision (including double vision), or a feeling that the eye is being pushed forward.
Vision changes and restricted eye movement are the most urgent red flags. They can indicate the infection has spread behind the eye, which requires imaging and prompt treatment. A stye that hasn’t improved at all after two weeks of warm compresses, or one that keeps coming back in the same spot, also warrants a closer look to rule out other causes of eyelid lumps.