A nail is a horn-like envelope covering the tips of the fingers and toes in most primates and a few other mammals. Nails are similar to claws in other animals. Fingernails and toenails are made of a tough protective protein called alpha-keratin. This protein is also found in the hooves and horns of different animals.
A comedo is a clogged hair follicle (pore) in the skin.[2] Keratin (skin debris) combines with oil to block the follicle.[3] A comedo can be open (blackhead) or closed by skin (whitehead), and occur with or without acne.[3] The word comedo comes from the Latin comedere, meaning “to eat up”, and was historically used to describe parasitic worms; in modern medical terminology, it is used to suggest the worm-like appearance of the expressed material.[1]
