What is the proper German term for 'blister'?

The proper German term for 'blister' is "Blase." This word specifically refers to a small pocket of fluid that forms on the skin, which is commonly known as a blister in English. It accurately describes the condition resulting from friction, burns, or other skin irritations that create a bubble-like formation filled with liquid.

The other terms listed do not correspond to 'blister.' "Grat" refers to a burr or edge, commonly in the context of metalwork or machining. "Chafing" is an English term that describes irritation or damage to the skin from rubbing, but it does not have a direct equivalent in German that relates specifically to the fluid-filled condition of a blister. "Buchse" translates to "sleeve" or "bushing," which is unrelated to skin conditions. Therefore, "Blase" is the correct term to use when referring to a blister in German.