Hair Biology FactsLaser Hair RemovalLaser Hair Removal Care
Hair Growth Cycle
A hair follicle is part of the skin that grows hair by packing old cells together to make a hair fiber. The hair follicle has three main regions: the infundibulum, isthmus, and hair bulb. The lower segment of the hair follicle is below the arrector pili muscle insertion. The hair follicle bulge, where a muscle called the arrector pili muscle attaches, is located between the skin surface and the follicle bulb, about one third of the distance from the skin surface. This bulge region contains adult stem cells that ensure the hair follicle survives throughout life. The hair bulb and dermal papilla form part of the inferior segment and it is in this region where most of the actual hair growing activity occurs. Usually the bulb is around 4-6mm from the surface of the skin.
Germinative matrix cells along with interspersed pigment producing melanocytes form part of the hair bulb. A cluster of cells called the dermal papilla in the hair bulb is responsible for nourishing the new hair fiber production through the blood vessels that pass through it.
The hair follicle bulb is also home to the dermal sheath cells and epidermal outer root cells. These cell types play an important part in hair growth by extending into the isthmus and infundibulum of the hair follicle and helping to protect the hair fiber is it forms and hardens.
Hair Growth Cycle
Each individual hair takes birth inside the hair bulb, a tiny but powerful factory. From birth to the end of life spanning decades or even a century, the follicle continues to produce hairs in a regular cycle. Somewhere between 10 and 20 hairs are produced by each hair follicle during a person’s life. Each scalp hair grows for between 2 and 6 years before falling out to be replaced by a new hair.
When the hair growth rate goes beyond the realm of normality or/and when they grow in places where they are not supposed to grow (in the case of women), laser surgery for permanent hair removal is required.
Stages of the Hair Growth
Human hair grows in distinct phases between the birth of hair and its eventual shedding. They are; the growth phase (anagen), the involutionary phase (catagen), and the end or resting stage (telogen).
The majority of the scalp follicles, at any particular time, (80–85%) are in the anagen phase and the remaining follicles are either in the catagen phase (2%) or the telogen phase (10–15%).
Anagen (The Growing Phase)
During the anagen phase there is very active growth in the hair bulb. Due to genetic or hormonal factors this phase is particularly responsible for excessive hair growth requiring laser surgery for permanent hair removal.
The anagen duration is affected by various factors such as age, season, gender, body site, hormones and genetic factors.
Melanin pigment production takes place during the anagen phase. Any damage during this phase can adversely influence the hair generation. Therefore, laser treatment is most effective during anagen.
Catagen (The Intermediate Phase)
A short resting phase termed the catagen phase follows the anagen phase. The catagen phase lasts for between two and four weeks. During catagen the hair follicle dismantles its hair fiber producing ability and becomes inactive.
Telogen (The Shedding Phase)
The duration of this telogen phase is about three or four months. Being the rest phase for the hair producing factory, no pigment is made during this phase and the follicle stops producing hair. During this period the base of the follicle comes closer to the surface of the skin. During the telogen phase the hair may be pulled out easily and painlessly. These are the hairs that come out during the brushing or shampooing of the hair.
After a telogen phase, the hair follicle returns to an anagen growth phase again. This new anagen phase involves the growing of new hair from the hair follicle. The new hair takes place of the old hair by emerging from the same opening at the surface of the skin as the old one, and the hair cycle begins again.
Shedding is quite normal as it happens because of the natural process of the replacement of old hair with new. At any particular time, around one in ten of the follicles are in the shedding phase.
Normally, activity of the hair follicle is not affected by anything. Save for dramatic changes such as harsh chemicals, exposure to radioactive substances, extreme heat, severe burns or scars etc., nothing that is applied to the scalp or hair can affect the growth of the hairs.
Laser surgery for permanent hair removal works on the principle of heating the follicle to destroy or severely damage the unwanted hair follicle and stop or significantly reduce its ability to make hair fiber.
Hair Biology Facts 