What is a chalazion? A chalazion is a blockage in a small duct in your eyelid that can result in a small bump and eyelid swelling. Each of your eyelids has small glands called meibomian glands located near the eyelashes, which produce one of the oils that lubricates your eye. When these glands cannot release their oil because their duct is blocked, the oil backs up and causes a bump. A chalazion is not the result of an infection, although it can follow an infection of the eye. An infection of these same small ducts is called a stye, which may resemble a chalazion but is usually quite painful and tender, while a chalazion is less painful. A chalazion can grow to the size of a marble in extreme circumstances. A chalazion is typically mild and requires no special treatment other than the application of a warm, damp compress several times a day to help loosen the oil blocking the duct. If a chalazion grows too large or cannot be resolved with a compress, it may be surgically removed. Seek prompt medical care if a bump on the eyelid remains for more than a month, if your vision is affected by the bump, or if the bump continues to grow despite treatment.