is a small collection of pus
in the top layer of skin
) or beneath it in the dermis
A papule is similar, but does not contain pus. The term pimple is used to describe pustules and papules collectively.
Pustules frequently form in sweat glands
or hair follicles
. They form when clogged pores rupture
under the surface. Usually found in oily areas. Also caused from clogged pores.