Eye styes form when bacteria, almost always Staphylococcus aureus, infect a blocked oil gland or hair follicle along your eyelid. The infection causes a painful, red bump that looks similar to a pimple. Most people get styes by transferring bacteria from their hands, nose, or contaminated items to their eyelids, though the specific trigger is usually a clogged gland that gives bacteria a place to multiply.
How the Infection Starts
Your eyelids contain dozens of tiny oil glands that keep your eyes lubricated. When one of these glands gets blocked by dead skin cells, dried oil, or debris, bacteria that normally live harmlessly on your skin can become trapped inside. The warm, sealed environment lets them multiply, and your immune system responds with inflammation, swelling, and pus.
The most common route is nose-to-eye. Staph bacteria live in the noses of many healthy people without causing problems. Rubbing your nose and then touching your eye transfers the bacteria directly to your eyelid, where it can colonize a blocked gland. This is why styes are so closely linked to hand hygiene.
External vs. Internal Styes
External styes appear along the edge of your eyelid, right at the base of an eyelash. They develop when the small oil glands (called glands of Zeis or Moll) near the lash line get infected. These are the more visible type and tend to come to a head and drain on their own.
Internal styes form deeper inside the eyelid, in the larger oil-producing glands embedded in the eyelid’s firm tissue. They’re often more painful because they press against the eyeball. When internal styes drain, they release pus on the inner surface of the eyelid rather than the outer skin. Internal styes can also take longer to resolve and are more likely to develop into a firm, painless lump called a chalazion if the gland stays blocked after the infection clears.
Common Causes and Risk Factors
Several everyday habits and conditions make styes more likely:
- Touching your eyes with unwashed hands. This is the single most common way bacteria reach your eyelid glands.
- Sleeping in eye makeup. Leftover mascara, eyeliner, and eyeshadow can clog the gland openings along your lash line. Cosmetics experts recommend replacing eye makeup every 3 to 4 months, since bacteria accumulate in the products over time.
- Wearing contact lenses improperly. Handling lenses without washing your hands first introduces bacteria directly to the eye area.
- Chronic eyelid inflammation (blepharitis). If you have ongoing redness, flaking, or irritation along your eyelid margins, the glands are more prone to blockage.
- Rosacea. This skin condition affects the oil glands throughout the face, including the eyelids, and increases stye risk.
Styes are more common in adults than in children. Adults produce thicker, more viscous oil in their skin glands due to higher hormone levels, which makes blockages more likely. Adults also have higher rates of chronic eyelid conditions like blepharitis and rosacea.
Can Stress Cause a Stye?
No study has directly linked stress to stye formation, but the connection isn’t far-fetched. Stress weakens your immune system’s ability to fight off bacterial infections. Research has shown that stress hormones can be converted into compounds that may actually attract bacteria to vulnerable areas of the body. Poor sleep, which often accompanies high stress, further lowers immune function by reducing the activity of infection-fighting T cells.
There’s also a behavioral component. When you’re exhausted or stressed, you’re less likely to remove makeup before bed, less careful about hand hygiene, and more likely to rub your eyes. These habits matter more than the stress itself.
Are Styes Contagious?
Styes are rarely contagious, but it’s not impossible. The bacteria inside a stye can spread through direct contact or shared items like towels and pillowcases. The risk is low in normal circumstances, but you should avoid sharing face towels or pillows with someone who has an active stye. Never squeeze or pop a stye, since the pus inside is packed with bacteria and can spread the infection across your eyelid or into the eye itself.
When a Stye Becomes Something More Serious
Most styes resolve on their own within a week or two with warm compresses. But in rare cases, the infection can spread beyond the gland into the surrounding eyelid tissue, causing a condition called preseptal cellulitis. This looks like widespread redness and swelling across the entire eyelid, not just a localized bump.
The signs that a stye has progressed to something requiring urgent attention include vision changes, double vision, limited ability to move the eye, or significant swelling that prevents you from opening the lid. Pain when moving the eye or a fever alongside eyelid swelling can indicate the infection has spread deeper into the eye socket, which is a medical emergency. These complications are uncommon, but recognizing them matters because they require prompt treatment to protect your vision.
Preventing Styes
Since most styes start with bacteria reaching a vulnerable gland, prevention comes down to keeping your eyelids clean and your hands away from your eyes. Wash your hands before touching your face. Remove all eye makeup before bed, and throw out mascara and eyeliner every three to four months. If you wear contacts, follow proper cleaning and handling protocols.
If you get styes repeatedly, a daily eyelid hygiene routine can help. Placing a warm, damp washcloth over your closed eyes for 5 to 10 minutes loosens oil in the glands and keeps them from clogging. Gently cleaning the lash line afterward with diluted baby shampoo or a commercial lid scrub removes debris and bacteria. People with blepharitis or rosacea benefit most from making this a daily habit rather than waiting for symptoms to appear.