A chalazion and a stye are both lumps in or along the edge of an eyelid. In some situations it may be difficult to distinguish between a chalazion
A stye often appears as a red, sore lump near the edge of the eyelid, caused by an infected eyelash follicle. When a stye occurs inside or under the
eyelid, it is called an internal hordeolum (pronounced "hor-dee-OH-lum").
The term chalazion (pronounced kuh-LAY-zee-un) comes from a Greek word meaning "small lump." A chalazion forms when an oil-producing gland
in the eyelid called the meibomian gland becomes enlarged and the gland opening becomes clogged with oil.
Chalazia tend to develop farther from the edge of the eyelid than styes. Often larger than stye, a chalazia usually isn't painful. It is not caused
by an infection from bacteria, and it is not a cancer. Sometimes, when a a stye doesn't heal, it can turn into a chalazion.
Visit the American Academy of Ophthalmology for more information on Stye and Chalazion.