Some parasites burrow under the skin very close to the surface - the snake-track-like lesions visible from the outside are described as "serpiginous."

There is also "intertrigo" (again pronounced with a stressed long i), the irritation that occurs when two patches of skin press against each other so consistently that they never have a chance to dry, and get all red and sore. ('"macerated," i.e. chewed up).

Btw - how come they put so many medical words on a high school kids' spelling bee list, anyway? :-)