The hair growth cycle has three phases: anagen or growth, catagen (transition between anagen and telogen) and telogen or resting. The length of the hair is proportional to the duration of the growth phase (which lasts between two and six years) . The longer this phase lasts, the more the hair will grow and “this depends on genetic, nutritional, hormonal and metabolic factors, ” explains Javier Olalquiaga, head of the Dermatology service at the Cemtro Clinic in Madrid. The speed and duration of the growth phase can vary according to age.
Elena Roche, specialist of the Hair Medicine Unit of Hospital Quirón in Valencia , specifies that hair grows depending on the level of blood flow, trace elements, amino acids and vitamins .
How much does it grow per day, month and year
According to her , hair grows about 0.4 millimeters a day, one centimeter a month and about 15 centimeters a year . Furthermore, “it tends to grow faster in adult women than in adult men, and with aging the growth rate decreases,” says Olalquiaga.
The growth is not homogeneous as in a particular area of the scalp will always be a percentage of hairs in each of the phases of the cycle.
“On the scalp and, in the absence of pathology, there are approximately 85 percent hairs in the anagen phase, 14 percent in catagen, and 1 percent in catagen.” Thus, for example, hair grows faster on the crown than in the temporal regions .
Olalquiaga points out situations in which the proportion of hair in the resting phase increases:
- Thyroid diseases
- Iron deficiency
- Hypozinchemia
- Febrile episodes
- Diets
- After delivery
Can you make it grow faster?
Roche reveals that the growth phase can be prolonged by using minoxidil . It blocks the action of a metabolite of testosterone at the level of the scalp, so that it reverses the miniaturization of the follicles (a process that causes baldness).
It denies that the greater or lesser care of the external hair influences the growth of the hair bulb. And Olalquiaga explains it: “growth takes place several millimeters deep.” Roche rules out that cutting or shaving hair makes it grow healthier and stronger.
