A sty looks like a small, red, pimple-like bump on the edge of your eyelid. It’s typically about the size of a pea, tender to the touch, and often develops a visible white or yellow head as pus collects inside. The surrounding eyelid usually swells and may appear puffy or discolored, sometimes enough that the bump itself is hard to pinpoint beneath the swelling.
How a Sty Develops Over Several Days
A sty doesn’t appear all at once. In the earliest stage, you’ll notice a tender, warm spot along your lash line before any visible bump forms. The skin in that area reddens and may feel slightly thickened or gritty, almost like something is stuck in your eye. Your eyelid might start watering more than usual.
Over the next three to five days, the bump itself takes shape. It grows into a firm, round nodule right at the eyelid margin, looking increasingly like a small boil. During this peak phase, a yellowish pustule often forms at the center of the bump as pus builds up. The whole eyelid can become swollen enough to partially close the eye. You may also notice crusting along the base of your eyelashes, especially after sleeping.
Most sties then drain on their own and resolve within one to two weeks total. Once the bump ruptures or the pus is reabsorbed, the swelling and redness gradually fade over a few more days.
External vs. Internal Sties
The bump most people picture is an external sty, which forms right at the base of an eyelash. It’s easy to spot because it sits on the outer skin surface of the eyelid, often with a clearly visible pus-filled head. When it drains, the material comes out along the lash line.
An internal sty looks different because it forms deeper inside the eyelid, in the oil glands embedded in the lid’s inner tissue. Instead of a distinct pimple on the skin, you’ll see a red, swollen area on the inside of the eyelid (visible when you gently flip the lid). From the outside, the eyelid may just look puffy and inflamed without an obvious bump. Internal sties tend to cause more diffuse swelling and can be more painful, occasionally causing enough inflammation to blur your vision temporarily or make the eye sensitive to light.
How to Tell a Sty From a Chalazion
A chalazion is the bump most commonly confused with a sty, and the two can look nearly identical in the early stages. The key differences are pain and position. A sty is very painful, red, and sits right at the eyelid’s edge, usually centered on an eyelash follicle. A chalazion tends to develop farther back on the eyelid, away from the lash line, and is typically not painful.
Timing also helps. A sty comes on quickly over a day or two with obvious tenderness and heat. A chalazion grows more slowly, and once it’s established, it feels firm and rubbery rather than soft and inflamed. Sometimes a sty that doesn’t fully drain turns into a chalazion: the infection clears, but a hard, painless lump remains where the blocked gland scarred over.
Secondary Signs Around the Eye
Beyond the bump itself, a sty often causes several changes to the surrounding eye that help identify it:
- Eyelid swelling that can extend well beyond the bump, sometimes making the whole upper or lower lid look puffy
- Crusting along the lash line, especially noticeable in the morning
- Excess tearing from the affected eye
- Warmth in the eyelid skin, which may feel noticeably hot compared to the other side
- A foreign body sensation, as if something is lodged in or scratching the eye
These signs usually stay localized to the affected eyelid. In some cases, you can develop more than one sty at the same time, or have sties on both eyes simultaneously, though a single bump is by far the most common presentation.
When a Sty Looks More Serious
A straightforward sty stays contained to a small area of the eyelid. If the redness and swelling start spreading beyond the eyelid itself, expanding toward the cheek, eyebrow, or across the bridge of the nose, that pattern suggests the infection may be moving into the surrounding tissue. This is a condition called preseptal cellulitis, and it looks distinctly different from a simple sty: the entire eyelid becomes deeply red and swollen shut, and the skin feels taut and hot over a wide area.
More concerning signs include the eye itself bulging forward, pain when moving the eye in any direction, changes in vision, or fever. These suggest the infection may have spread behind the eyelid into the eye socket, which requires urgent medical attention. A sty that has been present for more than a few weeks without improving, or one that keeps coming back in the same spot, also warrants a closer look from a doctor to rule out other types of eyelid lumps.