Styes are caused by bacterial infections in the tiny oil or sweat glands along your eyelid. When bacteria get into one of these glands, the area becomes inflamed and swollen, forming a painful red bump that looks similar to a pimple. The bacterium most commonly responsible is the same staph bacteria that lives on your skin all the time, which is why styes are so common and can seem to appear out of nowhere.
How a Stye Forms
Your eyelids contain several types of small glands that produce oils and moisture to keep your eyes lubricated. When one of these glands gets blocked or bacteria enter the opening, an infection takes hold and pus collects in the area. The result is the tender, swollen bump you recognize as a stye.
There are actually two types. An external stye forms right at the base of an eyelash, where oil and sweat glands sit close to the surface. These are the most recognizable kind: a visible, painful bump along the lash line. An internal stye develops deeper inside the eyelid, in the larger oil-producing glands embedded in the eyelid’s inner structure. Because of this deeper location, internal styes look less defined and may not be visible from the outside. Sometimes you can only see the small pus-filled spot by flipping the eyelid.
Everyday Triggers and Risk Factors
Anything that introduces bacteria to your eyelid or blocks those tiny glands raises your risk. The most common triggers are surprisingly mundane:
- Touching or rubbing your eyes with unwashed hands, which transfers bacteria directly to the eyelid
- Old makeup, especially mascara, which should be replaced at least every six months because bacteria grow in it over time
- Not removing makeup before bed, which can clog the glands along the lash line overnight
- Contact lenses handled without proper hygiene
- Dust and air pollution, which irritate the eyelid and make infection more likely
None of these guarantee a stye, but they create the conditions bacteria need to take hold. People who work in dusty environments or spend a lot of time touching their face tend to get styes more frequently.
Conditions That Cause Recurring Styes
If you keep getting styes, an underlying condition is likely involved. The most common culprit is blepharitis, a chronic inflammation of the eyelid margins. When the eyelid stays inflamed, the oil glands don’t function properly, making them easier targets for infection. Blepharitis often goes undiagnosed because its symptoms (slightly crusty, irritated eyelids) are easy to ignore.
Rosacea is another significant contributor that many people don’t connect to their eye problems. Ocular rosacea causes ongoing inflammation of the eyelid and tear film, and frequent styes are one of its hallmark signs. The condition involves an overactive immune response that produces excess inflammatory signals, disrupting the eyelid’s oil glands and the protective surface of the eye. People with ocular rosacea commonly deal with chronic red eyes, eyelid irritation, and recurring styes as part of an ongoing inflammatory cycle.
Tiny mites called Demodex, which naturally live on most people’s skin, can also play a role. When these mites overpopulate along the eyelashes, bacteria they carry can trigger inflammation and repeated infections. This is particularly common in people who already have rosacea or blepharitis.
What a Stye Feels Like
A stye is very painful. That’s one of its defining features. You’ll notice a red bump along the edge of your eyelid, often with a small white or yellow pus spot at the center. The entire eyelid can swell, and you may feel like something is stuck in your eye. Other common symptoms include a scratchy sensation, sensitivity to light, crustiness along the eyelid margin, and excessive tearing from that eye.
The pain and swelling typically peak in the first few days, then gradually improve. Most styes last one to two weeks and resolve on their own.
Styes vs. Chalazia
A chalazion is the bump people most commonly confuse with a stye, but the two have different causes and feel very different. A stye is a bacterial infection. A chalazion is a blocked oil gland without infection. The key distinction: chalazia are usually not painful. They tend to develop farther back on the eyelid, and you might not even notice one forming at first. A chalazion can grow large enough to press on the eyeball and blur your vision, which styes rarely do.
Sometimes a stye that doesn’t fully resolve can turn into a chalazion once the infection clears but the gland remains blocked. If you have a painless, firm bump on your eyelid that’s been there for weeks, it’s more likely a chalazion than a stye.
How Styes Heal
Most styes drain on their own within one to two weeks without any medical treatment. Warm compresses are the most effective way to speed things up. Holding a clean, warm washcloth against the closed eyelid helps the clogged gland open and drain. Doing this several times a day for 10 to 15 minutes per session softens the blockage and relieves discomfort.
Resist the urge to squeeze or pop a stye. Forcing it can spread the infection into surrounding tissue. Let it drain naturally, and keep the area clean.
When a Stye Becomes Serious
In rare cases, a stye infection can spread beyond the gland into the surrounding tissue of the eyelid, causing a condition called periorbital cellulitis. Signs that a stye has progressed include swelling that spreads across the entire eyelid or to the other eye, fever, or worsening redness that extends beyond the bump itself.
More concerning symptoms include double vision, a bulging eye, pain when moving the eye, or changes in vision. These suggest the infection has moved deeper into the eye socket, which requires urgent medical attention. This kind of progression is uncommon, but it’s worth knowing the warning signs, especially if a stye hasn’t improved at all after two to three days of warm compresses or is getting noticeably worse.
Preventing Styes
The simplest prevention comes down to keeping bacteria away from your eyelids. Wash your hands before touching your eyes or handling contact lenses. Replace mascara and eyeliner every six months. Remove all eye makeup before sleeping. When doing dusty yard work or similar tasks, wear protective glasses.
If you get styes frequently, washing your eyelids daily with diluted baby shampoo on a warm washcloth can help keep the glands clear and reduce bacterial buildup along the lash line. Treating any underlying blepharitis or rosacea also makes a significant difference in breaking the cycle of recurrence.