The growth phase (anagen phase): This is the phase in which a new hair root is formed and the hair begins to grow. A hair on the head grows around 0.4 millimeters per day – that corresponds to around 15 centimeters per year. A good 80 to 90 percent of the hair is in this phase. This lasts two to four years for men and four to six years for women. A hair root can develop ten to twelve hairs in a row and they fall out on the head after about seven years. Before this is the case, however, the hair has already gone through the transition phase (catagen phase) and the resting phase (telogen phase). The resting phase lasts about three to four months for hair on the head and twice as long for hair on the eyebrows. A fifth of the hair is in the resting phase and then falls out, making room for new hair.

Our hair grows the second fastest of all tissues in our body – only bone marrow grows even faster. But the speed of growth also depends on where a hair is located. A beard hair grows 2.8 millimeters per week, an armpit hair 2.1 millimeters in the same period and on the arm or thigh it grows around 1.5 millimeters per week. The eyebrow is the slowest, growing 1.1 millimeters in seven days.

Babies' bodies are covered with a fine down of hair called vellus hair. Babies born with thick head hair lose it until it grows back as terminal hair. Terminal hair is dense, strong hair containing pith and color pigments. With the exception of scalp hair, eyelashes and eyebrows, it is only formed at the onset of puberty. This is because the terminal hairs on the body only develop when androgens (sex hormones) begin to be released. Young women usually develop terminal hair on the arms/legs, armpits, and genital area. Men, on the other hand, also have chest, beard, belly, back and bottom hair and also terminal hair in the nose or in the ears. People who have excess body hair often suffer from diseases such as hirsutism (occurs only in women), hypertrichosis or atavism.

Body hair is a relic of our ancestors who needed fur to protect their skin. Since this protection is no longer necessary to the same extent today, the body only develops hair in those places where it is supposed to support temperature regulation (armpit hair) or provide additional protection (genital and anal areas).

Body hair removal has been a trend for many years. Studies show that more and more men and women value smooth, hairless skin. Permanent hair removal with IPL is also becoming increasingly popular, as this light technology removes hair over several growth cycles. For permanent hair removal with IPL, however, several treatments are necessary to really remove all the desired hair. This is because only those hairs that are in the growth phase can be removed per IPL treatment. As mentioned above, not all hair is in this phase at the same time, so the IPL treatment should be repeated after six to eight weeks.