What is a sty?
A sty (sometimes spelled “stye”) is a red, painful bump that forms either on or inside the eyelid near the edge of the eyelashes. A sty that appears on the outside of the upper or lower eyelid, the more usual location, is called an external sty. A sty that appears on the inside of the upper or lower eyelid is called an internal sty. A sty can look like an acne pimple.
The medical term for a sty is a hordeolum.
A sty is similar to another bump that occurs in the eyelid called a chalazion. A chalazion is a bump that usually occurs farther back on the eyelid. Unlike a sty, a chalazion is usually not painful and is not caused by a bacterial infection. Instead, a chalazion occurs when the opening of the oil-producing glands in the eyelid becomes clogged. Treatment for both conditions, however, is similar.
What causes a sty?
A sty is caused by a bacterial infection in the oil-producing glands in the eyelid. Oil-producing glands line the eyelids and help lubricate the surface of the eye.
What are the signs and symptoms of a sty?
Signs and symptoms of a sty include:
- Painful red bump along the edge of the upper or lower eyelid near the base of the eyelashes
- Swelling of the eyelid (sometimes the entire eyelid)
- Crusting along the eyelid
- Sensitivity to bright light
- Sore, scratchy eye
- Tearing of the eye
- A feeling that there is something in the eye