The material inside of a whitehead includes a collection of sebum oil, dead skin cells and bacteria. The sebaceous glands of the skin secrete oil into skin pores to help flush out dead skin cells. Too much sebum oil can lead to a blockage within the pore and cause a whitehead, according to Mayo Clinic.
A whitehead forms underneath the skin instead of on the surface. The texture of a whitehead is hard and these bumps can be difficult to pop without assistance from a dermatologist.
Pustules are often confused with whiteheads, but pustules are pimples filled with pus. These pop easily and are painful while a whitehead causes no pain.