It can be hard to tell, but there are differences. In general, a stye is infected and a chalazion is not. Infection can cause a small “pus spot” at the tip of a stye (shown here) that looks like a pimple. It can make your eye painful, crusty, scratchy, watery, and more sensitive to light. It may even make your whole eyelid swell. A chalazion usually doesn’t hurt and may make the eyelid swell early on. But you may not even notice it at first. If there’s no longer an infection, or the oil glands get clogged without being infected, it’s called a chalazion.