Is there a limit to the length that your hair will grow?
Sorting through some boxes the other day I came across some photos of me in my younger days. As was the fashion in the early to mid-1970s I took to wearing my hair long. There is part of me thinking that once I have released myself from the tyranny of the five-day a week working lifestyle I might just grow my hair long again and, perhaps, sport a pony tail. This may, of course, be a whim and I might get fed up with an untidy barnet before my hair gets to the requisite length.
This train of thought led me to consider, as you might expect, whether there is a natural and finite length that your hair will grow to. And, it seems, there is and it is all down to genetics and the three phases in the life-cycle of your follicles.
The first phase is known as the anagen phase. This, from the perspective of hair length, is the most important because it is the phase during which the follicle grows. How long the phase lasts is generally determined by your genetic make-up but can be affected by external factors such as stress or a hormonal imbalance. During this phase, which can last anywhere from between 2 to 7 years for the average person, your hair will generally grow at a rate of a centimetre every 28 days. The anagen phase comes to an end by the release of a signal, the cause of which has yet to be determined.
Once the chemical signal has been triggered your follicle goes into the catagen phase. The upshot is that the outer part of the root is shut off from its supply of blood upon which it relies for nutrients and the cells which are produced to aid growth. The result is that this phase signals the end of the follicle’s growing phase and in the average person it lasts about 3 weeks.
The final phase is the telogen phase. This is where the follicle is in what might be best described as a resting state and is effectively dead from the root up. It is follicles in this stage which come out when you comb your hair. If you don’t disturb them with a comb or a brush, they will eventually fall out.
It is estimated that at any point in time around 85 to 90% of your hair is in the anagen phase, around 1 to 2% is in the catagen phase and the balance is in the telogen phase. You can normally get a feel for how long your anagen phase will last without having to crop your follicles.
Of course, there are extremes at either end of the spectrum. Some people have extremely short anagen phases and, as a consequence, find it difficult to grow their hair. Extreme stress can cause the anagen phase to stop prematurely and increase the proportion of your follicles in the telogen phase dramatically, resulting in rapid hair loss. Others have prolonged anagen phases like Xie Quiping whose hair, when measured on 8th May 2004, was 18 feet 5.54 inches long!
Cutting your hair doesn’t upset the genetic make-up of your follicles. It just means that the follicles have to start all over again!
So now we know!