The human hair forms early in life
As a human fetus develops, forming all its vital organs and biological systems, so do all the hair follicles that this fetus will eventually have outside of the womb and on to adult life. A person has about 5 million follicles in the body and all these are well-formed at the fetal age of 22 weeks. Rarely do humans develop new hair follicles after this stage of development.
The anatomy of hair
Hair has two main parts – the hair shaft which is what we see on top of the skin, and the hair follicle which is under the skin.
The hair shaft is made up of scleroprotein, and is actually a dead structure. It has 3 layers. The inner layer is called the medulla which contains the pigment that gives hair its natural color. The middle layer is called the cortex which is responsible for some of the color and the thickness or body of the hair. The outer layer is the cuticle which, under the microscope, looks like overlapping shingles or scales.
From the cuticle of the hair shaft, the structure extends under the skin forming a section that is very much like a tube with a bulb at the bottom end. This is the hair follicle, the living part of the hair, which is made up of several components and layers. The dermal papilla is the part located at the bottom of the follicle, containing tiny blood vessels that provide nourishment to the cells. The bulb surrounds the papilla. Two sheaths surround the hair follicle and extend to protect the hair shaft.
The hair growth cycle
Human hair grows in a cycle with 3 stages – anagen, catagen and telogen.
Anagen is the active growth stage. It refers to the stage when the cells in the follicle divide quickly while extending the hair shaft. Hair in this stage is rich in protein, keratin and melanin. Hair stays on the skin or scalp while it is actively growing. On the average, hair grows roughly 1 centimeter in 28 days or 6 inches in a year. The active growth period for hair located on the head may last for 2-6 years. This long active growth stage explains why hair on the head can grow longer than hair elsewhere on the body. On the other hand, hairs on the legs, eyebrows and arms have much shorter active growth stage (just about 30-45 days), so they only grow a little over 1 centimeter before they progress to the next growth stage. About 85% of your hair is in the anagen stage at any given time.
Catagen is the transition stage where hair stops growing. Hair begins to move away from the papilla. This lasts for 1-3 weeks. Only about 3-4% of hairs will be in this phase before it moves to the next stage.
The resting phase of hair, or telogen stage, is when hair is pushed out and shed while new hair is being formed by the follicle. At this point, there is complete separation from the dermal papilla. This is the hair’s normal shedding as opposed to shedding resulting from laser or IPL treatment. Telogen hairs comprise around 10-13% of the body’s hair, and it’s quite normal to shed around 25-100 hairs every day. When new hair grows from the follicle, the cycle begins again.
How IPL and laser treatments remove hair permanently
Your unwanted hair will keep on growing back even when pulled, waxed, shaved or threaded. The reason is simple – you’re removing the dead part! The part that’s alive – the follicle – will keep producing hair shaft. This brings us to two of the latest methods in hair removal – laser and IPL hair removal treatment. They’re safe, effective, and virtually painless. The results are permanent because they destroy the hair follicles, not just the hair shaft.
Both laser and IPL hair removal treatments target the melanin in the hair. During the anagen stage, the hair’s matrix is securely connected to the hair follicle and the dermal papilla which provides nourishment to the hair. At this stage, hair has abundant supply of nutrients and melanin. Thus, anagen hairs will be most responsive to these treatments.
Once you undergo IPL or laser hair removal treatment, the anagen hair will be affected by the treatment and shed off days or weeks after. If you notice new hair growing after the treatment session, these are actually those hairs that were either in the catagen or telogen stages during the previous treatment. As they enter the anagen stage, they will become the target for the next treatment session and several sessions later. Treatment intervals are determined by taking into account the time it takes for the hair to enter another cycle, which is usually 6-8 weeks.