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Home » Why we are Peach Clinics » How Hair Grows

How hair grows has a lot more in common with your garden than just terminology.  Read on to find out more…

In the beginning…

Hair growth begins deep inside the hair follicle. Yet the only part of the hair defined as alive is at the very bottom of the follicle. This is the bulb.

The bulb, or hair root, contains the living cells that grow the hair while the visible part of the hair, the shaft, is already dead. Other important structures in the hair follicle include the sebaceous gland which produces oil to lubricate the hair; the arrector pili muscle which, when activated, will cause the hair to stand up (goose bumps); and the bulge.

Most importantly, the bulge is where cells stored to regenerate the bulb when it is lost at the end of each growth cycle abide. It is the bulge which needs targeting by any successful form of permanent hair removal.

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Hair Colours

hair colour All natural hair colours are the result of just 2 types of hair pigments and both of these are derivatives of melanin.

Eumelanin is the dominant pigment in brown and black hair, while pheomelanin is dominant in red hair. Blond hair is actually the result of having little pigmentation at all in the hair strand while grey and white hair occur when melanin production stops.

Hair thickness is simply determined by follicle size, not colour or curliness. Anyone’s hair volume can therefore be thin, normal, or thick from the same number of hairs of any colour.

Curly Hair

Curly haired girl The shape of the hair shaft has a direct effect on the curliness of your hair. A very round shaft resists movement with the same pressure in every direction encouraging it to remain straight.

Cross section curly, straight, wavy hair

The flatter or more elliptical the hair shaft becomes the curlier hair gets. Because the shape favours bending in one direction, the hair soon begins to curl after leaving the follicle.

Hair Types

Compare vellus and terminal hair Hair grows everywhere on the body except on mucus membranes and glabrous skin. Glabrous skin occurs in areas such as the palms of the hands, soles of the feet, and lips. As a new-born, we have all our hair follicles, but just one hair type grows in them: vellus hair.

Vellus hair is a fine, slow growing and almost transparent hair often simply called peach fuzz. The thicker, pigmented, faster-growing hair is called terminal hair. Over time, growth and sex hormones influence how hair grows. They cause hair follicles to switch production from vellus to terminal hair in the typical male and female hair growth patterns.

Hair Growth Cycle

hair growth cycle Hair follows a growth cycle with three distinct phases: anagen, catagen, and telogen. Importantly, all 3 occur simultaneously across the skin with each strand of hair on the body at its own phase of development. While one strand of hair may be in the anagen phase, another may be in the telogen phase.

The overall effect is for the volume of hair to appear constant despite some follicles being dormant (no hair) and others just beginning to grow new hair. The average rate of growth for hair is 1.25cm per month or 15cm per year.

Hair length owes more to the length of the Anagen (growing) phase than by the speed of hair growth. Scalp hair has the longest growth stage and is therefore capable of growing the longest hair while eyelashes and eyebrows have the fastest growth rate yet remain much shorter because of their brief growing phase.

Hair Growth Stages

follicle anatomy

Anagen Phase

The anagen phase is commonly known as the growth phase. This is the phase where the hair grows approximately 1cm per month. Hair on the scalp can grow for 2 – 6 years in anagen phase. At the other extreme, eyebrows will grow for just 4 – 8 weeks. The longer the hair stays in the anagen phase, the longer it will grow.

Catagen Phase

The catagen phase is also known as the transitional phase. During this time, which lasts about 2 weeks, the bulb detaches and “rests”. While remaining in the follicle, the hair strand is cut off from its nourishing blood supply and stops growing.

Telogen Phase

During the telogen, or resting phase, the follicle remains dormant for 1 – 4 months. Around 10% – 15% of scalp hair is in this phase of growth at any given time. Now the follicle lining is all that temporarily anchors the hair in place. Eventually the hair will work its way free and the hair will be shed. Within weeks, a new hair shaft will begin to emerge and the cycle begins again.

Significance of the Bulge

It’s all about the stem cells

Early researchers theorised that hair grew back from the root or bulb of the hair and that destroying the root would destroy the hair forever. Experience has demonstrated that damaging the root and its blood supply does not destroy the follicle’s ability to regenerate a hair. It merely delays the process until the body repairs the blood supply to the follicle.

With the discovery of the role of stem cells, later researchers went looking for stem cells in the root of the hair at the base of the follicle. Instead, they found them in the bulge located half way up the follicle near the arrector pili muscle (the muscle that makes your hair stand on end). Significantly for treatment methods, the bulge is transparent and has no contact with the hair for most of the growth cycle.

Why Galvanic Electrolysis is permanent

In galvanic electrolysis, a small electric current passes through a thin metal probe into the hair follicle. This converts salty water in the follicle into sodium hydroxide using the electrochemical effect called electrolysis. This sodium hydroxide is able to completely destroy the contents and lining of the follicle. Most importantly, it destroys the bulge and its stem cells responsible for producing new hairs. The probe is then removed along with the hair and the follicle contents. This is how electrolysis achieves permanent hair removal.

Because sodium hydroxide is able to circulate throughout the follicle, it is able to destroy all its contents from top to bottom and works no matter what stage of the growth cycle the hair is in.

Why Thermolysis is not as effective as Electrolysis

In Thermolysis (known commonly as single needle electrolysis) a small probe inserted into each follicle transmits microwave radiation down to the root of the hair. This radiation works on the same principle as a microwave oven and heats the hair root to about 48°C to 50°C causing electrocoagulation. This rapid increase in temperature causes coagulation of the proteins within the cells, effectively killing the root.

With Thermolysis, heat concentrates around the root and not at the level of the bulge. The only time that Thermolysis can be permanently effective is during early anagen stage when the hair root rises to be adjacent to the bulge. During this brief time, the bulge connects to the hair root and heat in the root conducts to the bulge with the ability to damage or destroy it. This robs the follicle of its ability to grow another hair.

In practice, around 90% of Thermolysis treated hairs will have regrown after 3 months and perhaps 10% permanently destroyed. This means going back over the same hairs, time and time again, thinning them out by 10% at each treatment because the bulge and its stem cells are not in contact with the hair itself and remain immune to the heat produced by Thermolysis.

Why Laser and IPL are not as effective as Electrolysis

Again, Laser can remove existing visible hair, but only permanently destroy 1 in 6 hairs at each treatment. For this reason, the Therapeutic Goods Administration (TGA) in America only permits Laser and Thermolysis to describe themselves as “permanent hair reduction”. These poor results from Laser are because the bulge and its stem cells are relatively transparent and therefore immune to heating by laser light.

During early anagen stage when the hair root rises to be adjacent to the bulge, the bulge is connects with the hair root and heat from the Laser conducts from the root to the bulge with the ability to damage or destroy it. This robs the follicle of its ability to grow another hair.