A stye is caused by a bacterial infection in one of the small glands along your eyelid. In 90% to 95% of cases, the specific bacterium responsible is Staphylococcus aureus, a common species that lives on your skin and can slip into a gland when conditions are right. The infection creates a painful, red bump that fills with pus, similar to a small abscess.
How the Infection Starts
Your eyelids contain dozens of tiny glands that produce oils and sweat to keep your eyes lubricated. When one of these glands gets clogged by dead skin cells, dried oil, or debris, bacteria that normally sit harmlessly on your skin can multiply inside the blocked gland. The result is a localized infection: swelling, redness, tenderness, and eventually a visible pus-filled bump.
There are two types depending on which gland is affected. An external stye forms at the base of an eyelash, where small oil and sweat glands sit right along the eyelid margin. This is the classic stye most people picture: a painful pustule at the edge of the lid. An internal stye develops deeper inside the eyelid, in the meibomian glands. These larger oil glands are embedded in the firm tissue of the lid itself and produce the oily layer of your tear film. Internal styes tend to be less visible from the outside but can cause significant swelling and discomfort.
Common Triggers
The bacterium that causes styes is already on most people’s skin. What determines whether you get a stye is usually whether something gives those bacteria an easy path into a gland. The most common everyday triggers include:
- Touching or rubbing your eyes with unwashed hands, which transfers bacteria directly to the eyelid margin
- Old or shared eye makeup. Mascara and eyeliner can harbor bacteria after just one use. Experts recommend replacing eye cosmetics every 3 to 4 months and never sharing brushes or applicators.
- Sleeping in contact lenses or handling them without clean hands, which introduces bacteria and traps them against the eye
- Improper cosmetic storage. Keeping makeup above 85°F (such as in a hot car) weakens preservatives and encourages bacterial growth.
- Not removing makeup before bed, which clogs the oil glands along the lash line overnight
Conditions That Make Styes More Likely
Some people get styes repeatedly, and that pattern often points to an underlying eyelid condition rather than bad luck. Blepharitis, a chronic low-grade inflammation of the eyelid margins, is one of the most common culprits. When the eyelid margins are constantly irritated, the oil glands don’t drain properly, creating a breeding ground for infection.
Ocular rosacea is another frequent driver of recurrent styes. This condition causes ongoing inflammation of the eyelid and disrupts the meibomian glands, leading to both styes and chalazia (painless blocked glands). If you notice persistent redness, dryness, or irritation in your eyes alongside repeated styes, ocular rosacea or blepharitis may be the root cause. People with skin conditions like seborrheic dermatitis or acne rosacea on their face are at higher risk.
What a Stye Feels Like
A stye typically starts as a tender, slightly swollen spot on the eyelid that becomes increasingly painful over a day or two. As it develops, you may notice a small yellow or white pus spot at the center of the bump, crusting along the lash line, tearing, light sensitivity, and a gritty or scratchy feeling like something is stuck in your eye. External styes can sometimes make the entire eyelid swell.
Stye vs. Chalazion
Not every bump on the eyelid is a stye. A chalazion looks similar but develops differently. A stye is an active infection: it hurts, appears at the eyelid edge near the lashes, and often makes the whole lid puffy. A chalazion is a blocked oil gland without an active infection. It usually forms farther back on the lid, is rarely painful, and grows more gradually. A chalazion can cause blurry vision if it gets large enough to press on the eyeball, but it doesn’t produce the sharp tenderness of a stye. Sometimes a stye that doesn’t fully drain turns into a chalazion as the inflammation becomes chronic.
How Styes Heal
Most styes resolve on their own within one to two weeks. The standard home treatment is a warm, moist compress held against the closed eyelid for 5 to 10 minutes, repeated 3 to 6 times a day. The warmth helps soften the clogged material inside the gland and encourages the stye to drain naturally. Use a clean cloth soaked in warm (not hot) water. Microwaving a wet cloth is not recommended because it can overheat unevenly and burn the delicate eyelid skin.
Resist the urge to squeeze or pop a stye. Forcing it open can spread the infection into surrounding tissue. Let it come to a head and drain on its own. Keep the area clean, avoid wearing eye makeup or contact lenses while you have an active stye, and wash your hands before touching anywhere near your eyes.
When a Stye Becomes Serious
Rarely, a stye can progress to a more widespread infection called preseptal cellulitis, where the skin and tissue around the eye become red, swollen, and warm. This condition is treatable but needs prompt medical attention. Warning signs include swelling that spreads well beyond the bump, fever, or increasing pain that doesn’t improve after several days of warm compresses.
If the infection spreads deeper into the eye socket itself (orbital cellulitis), symptoms escalate significantly: the eye may bulge forward, vision can decrease, and it may hurt to move the eye. This is a medical emergency. Fortunately, progressing from a simple stye to orbital cellulitis is rare, but knowing the difference between normal stye discomfort and these warning signs matters.
Preventing Styes
Since the underlying cause is bacteria entering a clogged gland, prevention comes down to keeping your eyelids clean and minimizing the bacteria you introduce. Wash your hands before touching your face. Replace mascara and eyeliner every few months. Remove all eye makeup before sleep. If you wear contacts, follow the cleaning schedule and never sleep in lenses not designed for overnight wear.
For people prone to recurrent styes, a daily eyelid hygiene routine can make a real difference. Gently cleaning the lash line with warm water or a diluted baby shampoo solution helps prevent the oil glands from clogging in the first place. If styes keep coming back despite good hygiene, it’s worth having an eye doctor evaluate for blepharitis or ocular rosacea, since treating the underlying inflammation can break the cycle.