A stye forms when bacteria, almost always Staphylococcus aureus (the same germ behind staph infections), get into one of the tiny oil glands along your eyelid margin and cause an infection. The result is a small, painful abscess that looks like a pimple at the base of an eyelash. Styes are one of the most common eyelid problems, they affect men and women equally, and they’re more common in adults than children.
What Actually Happens Inside Your Eyelid
Your eyelids contain dozens of small oil glands whose job is to coat the surface of your eye with a thin layer of oil every time you blink. These glands drain through narrow ducts that open near your eyelashes. When debris, dead skin cells, dried oil, or bacteria block one of those ducts, the oil backs up and creates the perfect environment for staph bacteria to multiply. The gland swells, fills with pus, and becomes the tender red bump you recognize as a stye.
An external stye, which is the most common type, develops right at the eyelid margin near the base of a lash. Within a day or two you’ll typically see a small yellowish head surrounded by redness and swelling. An internal stye develops deeper in the eyelid, inside a larger oil gland on the inner surface. Internal styes are less visible but can be more painful, and in rare cases cause fever or chills because the inflammation is more intense.
Common Causes and Risk Factors
Most styes come down to bacteria reaching a blocked gland. But several everyday habits and conditions make that more likely:
- Touching your eyes with unwashed hands. This is the single most direct way staph bacteria from your skin, nose, or surroundings reach your eyelids.
- Old or contaminated eye makeup. Mascara, eyeliner, and eyeshadow collect bacteria over time. Replacing eye makeup every three months significantly reduces your risk.
- Contact lens habits. Handling lenses without washing your hands first, or wearing them longer than recommended, introduces bacteria to the eye area.
- Blepharitis. This is chronic low-grade inflammation of the eyelid margins that causes flaky, irritated lids. It keeps the oil glands partially blocked and creates ongoing conditions for infection.
- Rosacea. People with rosacea frequently develop a related condition called ocular rosacea that inflames the eyelid glands. A study using the Rochester Epidemiology Project found that children who had styes were significantly more likely to develop rosacea as adults (5.5% versus 1.5% in controls), suggesting a shared underlying tendency toward gland inflammation.
Adults get styes more often than children, likely because adult skin produces thicker oil that clogs glands more easily, and because conditions like blepharitis and rosacea become more common with age. There’s no difference in risk across racial groups.
What a Stye Feels and Looks Like
The first sign is usually tenderness and slight swelling at one spot on your eyelid. Over the next day or two, that spot becomes redder and more swollen, and you may notice your whole eyelid feels puffy. An external stye develops a visible white or yellowish head, much like a pimple, right at the lash line. It’s often sore enough that blinking feels uncomfortable.
Most styes last one to two weeks and drain on their own without treatment. The key comfort measure is a warm compress: a clean washcloth soaked in warm water, held against the closed eyelid for 10 to 15 minutes several times a day. The warmth loosens the blocked oil and encourages the stye to drain naturally. If pain and swelling haven’t started improving after 48 hours of warm compresses, that’s a good signal to have it looked at.
Stye vs. Chalazion
In the first day or two, a stye and a chalazion look almost identical: both cause a sore, swollen bump on the eyelid. The difference is that a stye is an active bacterial infection, while a chalazion is a blocked gland without infection. Their paths diverge quickly. A stye stays painful and camps out right at the eyelid edge, often with a visible pus-filled head. A chalazion migrates toward the center of the eyelid and becomes a firm, painless nodule within a couple of days.
This distinction matters because styes usually resolve faster and respond well to warm compresses alone, while chalazia can linger for weeks or months and occasionally need a minor in-office procedure to drain.
When a Stye Becomes Something More Serious
Styes rarely cause complications, but an untreated infection can occasionally spread to the surrounding tissue. The condition to watch for is called preseptal cellulitis, an infection of the soft tissue around the eye. Signs include spreading redness and warmth beyond the original bump, significant swelling that makes it hard to open your eye, and fever.
A more serious but much rarer progression is orbital cellulitis, where infection reaches the deeper tissues behind the eye. This causes pain with eye movement, reduced vision, and the eye may appear to bulge forward. Headache and unusual drowsiness alongside these symptoms warrant urgent medical attention, as the infection can spread further. These complications are uncommon, but recognizing the warning signs, especially worsening swelling, fever, vision changes, or pain with eye movement, helps you act quickly if a simple stye takes a wrong turn.
How to Reduce Your Risk
Because styes start with bacteria meeting a blocked gland, prevention targets both sides of that equation. Washing your hands before touching your face or handling contact lenses removes the bacteria. Replacing eye makeup every three months and never sharing mascara or eyeliner prevents contaminated products from delivering bacteria directly to the lash line. Removing all eye makeup before bed keeps the gland openings clear overnight, when oil production continues but you’re not blinking it away.
If you get styes repeatedly, the underlying issue is often chronic eyelid inflammation. A daily lid hygiene routine, gently cleaning the lash line with a warm washcloth or diluted baby shampoo, helps keep the oil glands flowing freely and breaks the cycle of blockage and infection.