Styes are caused by bacterial infection of the oil glands in your eyelid, almost always by Staphylococcus aureus, the same bacteria behind common staph infections. When one of these tiny glands gets blocked, bacteria multiply inside it, creating a painful, red bump along your lash line. Most styes resolve on their own within one to two weeks, but understanding what triggers them can help you avoid repeat episodes.
How a Stye Forms
Your eyelids contain dozens of small oil glands that help lubricate your eyes. These glands produce natural oils that drain through narrow ducts onto your eyelashes. When debris, dead skin cells, or dried oil blocks one of those ducts, bacteria that normally live harmlessly on your skin get trapped inside and multiply. The result is a small abscess: a stye.
There are two types, depending on which glands are involved. External styes form in the smaller glands (called Zeis or Moll glands) right at the base of your eyelashes, so they appear as a visible bump on the outer edge of the lid. Internal styes form deeper inside the eyelid, in the larger oil-producing glands embedded in the lid itself. Internal styes tend to be more painful and less visible from the outside, though the lid often swells noticeably.
Touching Your Eyes With Dirty Hands
This is the most common and preventable trigger. Every time you rub your eyes or adjust your contact lenses without washing your hands, you transfer bacteria directly to your eyelid glands. It only takes a small amount of staph bacteria introduced to an already sluggish gland to start an infection. If you wear contacts, the risk compounds because you’re touching your eye surface multiple times a day.
Old or Contaminated Makeup
Eye makeup is one of the most overlooked causes of styes. Mascara, eyeliner, and eyeshadow sit in warm, dark tubes and palettes where bacteria thrive over time. Experts recommend replacing eye cosmetics every three to four months, even if they still look and smell fine. Beyond age, how you handle makeup matters just as much. Sharing eye products introduces someone else’s bacteria to your lids. Spitting into dried-out mascara to moisten it seeds the product with mouth bacteria. And applying makeup in a moving car risks not just injury but contamination from touching your face and eyes with unsteady hands.
A few specific habits raise your risk:
- Sleeping in makeup. Leaving eye makeup on overnight gives bacteria hours of uninterrupted contact with your gland openings.
- Using glitter or metallic eyeshadow. Small flakes can fall into the eye, irritating the lid margin and creating entry points for infection.
- Dirty applicator tools. Brushes, sponges, and eyelash curlers accumulate bacteria with every use and should be cleaned regularly.
Blepharitis and Chronic Lid Inflammation
Blepharitis is a condition where the edges of your eyelids stay chronically inflamed, often with flaky, dandruff-like debris at the base of your lashes. This ongoing inflammation disrupts the normal flow of oil from your glands, making blockages far more likely. People with blepharitis often get styes repeatedly because the underlying gland dysfunction never fully resolves between episodes. If you find yourself getting styes more than once or twice a year, chronic lid inflammation is one of the first things to investigate.
Skin Conditions That Affect the Eyelids
Rosacea and seborrheic dermatitis both alter the quality and flow of oil on your skin, including the delicate skin of your eyelids. Rosacea in particular has a well-established connection to a subtype called ocular rosacea, which causes gland dysfunction very similar to blepharitis. People with these conditions produce thicker, stickier oil that clogs gland openings more easily, setting the stage for bacterial overgrowth.
High Blood Sugar and Diabetes
Uncontrolled diabetes creates a double problem. High blood sugar triggers the production of molecules that suppress your body’s immune defenses, making it harder to fight off the staph bacteria that cause styes. At the same time, the metabolic changes associated with poorly managed blood sugar can affect the composition of oils your glands produce. The result is that people with uncontrolled diabetes are more prone to infections generally, and styes specifically. If you’re diabetic and notice recurring styes, it may be a signal that your blood sugar management needs attention.
Stress and Sleep Deprivation
When you’re sleep-deprived or under prolonged stress, your immune system becomes less efficient at keeping normal skin bacteria in check. Staph bacteria are already present on most people’s eyelids without causing problems. The difference between carrying those bacteria harmlessly and developing an active infection often comes down to immune function. Periods of high stress, illness, or poor sleep can tip that balance.
How to Reduce Your Risk
The single most effective prevention strategy is keeping your eyelids clean. If you’re prone to styes, using a warm compress or heated eye mask for about 10 minutes at a time helps keep the oil glands flowing freely. Doing this regularly, not just when a stye appears, reduces the chance of blockages forming in the first place. Always wash your hands thoroughly before touching your eyes for any reason, whether you’re putting in contacts, applying makeup, or just rubbing an itch.
Replace eye cosmetics every three to four months. Remove all eye makeup before bed every night. Keep brushes and applicators clean, and never share eye products. If you’ve had a stye recently, consider discarding any makeup you used in the days before it appeared, since the product itself may be harboring the bacteria that caused it.
For people with blepharitis or rosacea, daily lid hygiene with a gentle cleanser designed for the eyelid margin can make a significant difference in how often styes recur. Warm compresses soften the thickened oils that tend to block glands in these conditions, and consistent use over weeks and months is more effective than occasional treatment.