CAREERS OF THE NAILS & HAIR
Dermatology is the study of the skin. A dermatologist, though a doctor of the skin, can also help you with hair or nail problems (since many of the problems relate to the skin).
A manicurist is a person who trims and cleans nails.
Cosmetology is associated with appearance and wellness. In some cases, a cosmetologist is a person who cuts, washes, and/or styles hair. Other cosmetologists may also specialize in skin care. (There are many fields of cosmetology.)
There is only when more section to discuss: the skin.