blister

A blister is that painful, fluid-filled pocket that forms on your skin after repeated rubbing—think new shoes on a long hike. It's your body's way of protecting the delicate tissue underneath. While friction is the usual cause, heat, chemicals, and cold can also trigger one. Imagine a tiny bubble of protection forming between your heel and sock on a hard walk. It may be tempting to pop it, but it's usually best to let it heal unless it becomes very painful or dirty.

The word isn't only for skin, though. It also describes bubbles on painted walls or timber when heat or moisture gets trapped beneath the surface. Figuratively, "blistering" means something severe or harsh, like a "blistering sun" or a "blistering critique" that leaves someone stung.

A blister is most commonly a small pocket of fluid—usually serum, plasma, or blood—that forms within the upper layers of skin. This happens when friction, pressure, heat, or chemical exposure damages tissue. Think of breaking in new leather boots: repeated rubbing creates those familiar, uncomfortable bubbles. In most cases, the body creates this pocket as a protective cushion to reduce further damage and give new skin time to recover.

The term also appears in materials and construction. If paint on a wall or a boat hull bubbles or lifts, that's often called blistering, usually from trapped moisture, heat, or gas. In these settings, "blister" refers to an unwanted surface defect.

It also has figurative uses. As a verb, "to blister" means to scald or to criticize someone in a sharp, cutting way: "The coach blistered the team for poor effort." As an adjective, "blistering" describes something extreme—very hot, very fast, or very fierce—like a "blistering sun" or a "blistering pace."