Styes are caused by bacterial infections in the oil glands of your eyelid, with staphylococcus bacteria responsible for most cases. These glands normally produce oil that coats your tears and keeps your eyes from drying out, but when one gets clogged, bacteria already living on your skin can multiply inside it and trigger a painful, red bump.
How a Stye Forms
Your eyelids contain dozens of tiny oil glands, called meibomian glands, along with smaller glands at the base of each eyelash. These glands release a thin layer of oil every time you blink. When one of these glands gets blocked, oil backs up inside it. That trapped oil creates a warm, enclosed environment where staph bacteria, which naturally live on your skin and eyelashes, can thrive. The result is a localized infection: swelling, redness, tenderness, and often a visible white or yellow head at the surface.
A stye at the edge of your eyelid (an external stye) usually starts at an infected eyelash root. One deeper inside the lid (an internal stye) forms when a meibomian gland itself becomes infected. Both follow the same basic pattern of blockage followed by bacterial overgrowth, but internal styes tend to be more painful because the infection sits against the eyeball.
Styes vs. Chalazia
Not every eyelid bump is a stye. A chalazion develops when a blocked gland becomes inflamed but not actively infected. The key differences: a stye is very painful and typically appears at the eyelid’s edge, while a chalazion usually isn’t painful and forms farther back on the lid. Chalazia tend to grow larger and more slowly. A stye can sometimes turn into a chalazion if the infection clears but the gland remains blocked.
Risk Factors and Common Triggers
Anything that blocks your eyelid glands or introduces bacteria to the area raises your chances of getting a stye. The most common triggers fall into a few categories.
Touching Your Eyes
Rubbing your eyes with unwashed hands is one of the fastest ways to transfer staph bacteria directly to the oil glands. This is especially true if you wear contact lenses and handle them without washing your hands first.
Old or Shared Makeup
Your eyelashes naturally carry bacteria. The moment a mascara wand or eyeliner brush touches your lashes, it picks up those bacteria and deposits them back into the product container. Over time, bacterial levels build up in the cosmetic itself, increasing the infection risk with each use. Experts suggest replacing eye makeup every three to four months. Sharing brushes or eyeliners with others compounds the problem by introducing new bacterial strains. Storing cosmetics above 85°F (such as in a hot car) also weakens the preservatives that keep bacteria in check.
Chronic Eyelid Conditions
People with blepharitis, a condition where the eyelids are chronically inflamed, are significantly more prone to recurrent styes. The inflammation disrupts normal oil gland function, making blockages more likely. Ocular rosacea works through a similar mechanism. In fact, styes and blocked oil glands are among the most common symptoms of ocular rosacea, and some clinicians consider ocular rosacea and meibomian gland dysfunction to be closely overlapping conditions.
Age and Hormones
Styes are more common in adults than in children. One reason is that adult hormone levels (particularly androgens) increase the thickness of the oil these glands produce, making blockages more likely. Adults also have higher rates of chronic eyelid inflammation and rosacea, both of which feed the cycle. That said, children can and do get styes. There’s no difference in rates between men and women or across racial groups.
Why Some People Get Styes Repeatedly
If you keep getting styes, the underlying cause is usually not a single episode of bad luck but an ongoing problem with your oil glands. Meibomian gland dysfunction, where the glands chronically fail to release oil properly, is the most common culprit. When these glands aren’t working well, they stay partially blocked much of the time, giving bacteria repeated opportunities to cause infection. Untreated blepharitis or rosacea keeps the cycle going. Stress and sleep deprivation may also play a role by suppressing your immune system’s ability to fight off minor skin infections before they take hold.
People who wear contact lenses, skip removing eye makeup before bed, or have oily skin also tend to experience styes more frequently. In many cases, it’s a combination of factors rather than a single cause.
What Happens as a Stye Heals
Most styes resolve on their own within one to two weeks. The standard home treatment is a warm compress: a clean washcloth soaked in warm water and placed gently over the closed eye for five minutes, several times a day. The warmth helps loosen the blocked oil, encourages the gland to drain, and increases blood flow to the area so your immune system can clear the infection.
You should avoid squeezing or popping a stye, which can push the infection deeper into the lid. If a stye hasn’t started improving after a week of consistent warm compresses, it may need professional attention. In some cases, a doctor will drain it with a small incision or prescribe a topical antibiotic if the infection is spreading beyond the original bump.
Signs of a More Serious Infection
Styes very rarely lead to dangerous complications, but it’s worth knowing the warning signs. If swelling spreads beyond your eyelid to the skin around your eye, if you develop a fever, or if your eye begins to bulge or becomes difficult to move, the infection may have spread to the deeper tissues around your eye socket. This condition, called orbital cellulitis, requires urgent medical treatment. Vision changes, intense pain with eye movement, or redness that extends well beyond the lid are all reasons to seek care quickly, particularly in children.