A welt is a raised mark or ridge on the skin, often red and slightly swollen, that appears after being hit or stung. If a baseball smacks your arm, you might see a welt form where it struck. Mosquito bites leave small welts that itch. A bee sting can create a painful welt that might throb for hours.

Welts can come from insect bites, allergic reactions, or impacts. They're your body's response to injury or irritation: blood rushes to the area, causing swelling and that characteristic raised bump. Some welts fade quickly, while others last for days.

The word also describes a similar ridge or seam in other contexts. A welt on a shoe is the strip of leather that joins the upper part to the sole, creating a visible ridge. On upholstered furniture, decorative welting (also called piping) creates raised seams where fabric pieces meet, giving chairs and cushions a finished, professional look.