Hair is a type of protein that is part of the integumentary system. Hair grows out of hair follicles embedded deep inside the skin. The hair shaft is made up of dead hair cells, and the only part of the hair that contains living cells is the root. Hair is classified into three groups: terminal, vellus and lanugo. Terminal hair is the fully developed, thick, coarse hair found on the head, underarms and pubic area. Vellus hair is the short, very fine hair also called "peach fuzz" that covers almost every part of the human body except the palms of the hands, soles of the feet and lips. Lanugo hair is the hair that covers a fetus, and is also sometimes found on anorexics or malnourished people as a way to retain heat.
Hair grows according to its predetermined genetic structure, and no amount of cutting or trimming can induce hair to grow faster than a person's genetic code dictates. Cutting or trimming hair will only affect the hair's bulkiness, making it appear thicker or finer based on the style of the haircut. A blunt cut will make hair appear thicker, while a layered cut will make hair appear finer. In prepubescent children, hair growth often coincides with general growth spurts. Thus, it may appear that at times a child's hair grows extremely rapidly, while at other times it does not seem to grow at all. Some people's genes might make their hair grow faster or slower than others'.
Generally, hair grows half an inch per month whether or not it is trimmed or cut often. Hair may grow slightly faster in the summer, but that is a result of hormonal changes that occur during the warmer months. Hair growth is not easily influenced by outside factors, however, hair loss can be more vulnerable to external forces. One of the major factors influencing hair loss is stress. Stressful situations such as divorce, loss of a job or loss of a loved one can result in hair loss. Generally, there is no way to make hair grow faster than it does.