Why would you get random blisters around the ankle?

Sweat: From sweat or swelling inside your skin.

A touchy feely thing: There are many causes for blister formation, but the list gets a whole lot shorter when the blistering is confined to small area. The search is now limited to the source of the blister forming element. More than likely, it involves a reaction to touching something that induced a tissue reaction. My guess it's either animal, vegetable or mineral. Go figure.