The hair cycle plays a major role in treatment effectiveness. In fact, lasers are most effective during the growth period because it is at this precise moment that the hair root has a high concentration of melanin. This melanin is the most important element to the success of the treatment, since it absorbs the laser, which instantly turns into heat and disintegrates the hair.
All hairs have the same life cycle, but they do not go through the same phases at the same time, unlike animals, which have clearly defined moulting periods. It is also important to note that in certain areas the length of the hair’s life cycle is different: the hairs in the upper lip area have a life cycle that lasts 5 months, while leg hair has a life span of around 18 to 24 months. A person’s age and sex also influence the length of the hair cycle. It’s all a matter of hormones.
Located 1.5 mm from the surface of the skin, the hair cycle starts in the matrix where the root of the hair is formed.
- The anagen phase:
this is the period of hair growth when the concentration of melanin is highest, and during which hair removal is effective. There is a particularly high concentration of melanin at this time because hair pigmentation is determined in this period. This phase involves about 25% of the hairs during a hair removal session, which is the percentage of hairs that are successfully destroyed. The dermal papilla nourishes the hair to make it grow during this phase, which lasts from 1 to 3 months.
- The catagen phase:
this is the hair’s cell resting period, which stops any growth processes. This relatively short phase lasts around 3 weeks. At that time, the hair detaches itself from its source of nutrition to halt its development. As a result, there is a low concentration of melanin in the root, which is why it is almost ineffective to use lasers in this phase.
- The telogen phase:
this is the final stage in the hair’s life cycle to make way for a new hair to grow in its place. The laser is not at all effective during this period, which lasts between 3 and 4 months because melanin is almost non-existent. The new hair in the anagen phase gradually pushes the hair in the telogen phase, eventually making it fall out.