Swollen lips may be caused by allergic reactions, injuries, chapping or sunburn, infections, and cysts called mucoceles. The swelling comes from either inflammation or built-up fluid under the skin.

Have you ever eaten something spicy and felt that tingly, swollen-like sensation? That's kind of what sunburned lips feel like. "Sunburned lips are red, swollen, and painful," says Kenneth Howe, MD, ...