Why does my hair always stop growing once it gets to a certain length

00:00 Mon 05th Nov 2001 The AnswerBank

A. The maximum length your hair can grow is determined by your genetic make up, so I'm afraid there is little you can do about it.


Hair grows in a cycle, which is divided into three stages: the anagen phase, the catagen phase and the telogen phase.


Q. I never knew it was so involved, what defines each stage

A. During the anagen phase, which lasts from 3 to 5 years, protein and keratin are continuously made and your hair grows. At any one time 90% of the hair on your head is in the anagen phase.


During the catagen phase, which lasts around three weeks, your hair follicle undergoes structural and chemical changes which breaks the hair shaft and the hair stops growing.


Finally, during the telogen phase, your hair stays put on your head for around three months. At the end of this phase it falls out as the next budding hair that is at the start of its anagen phase replaces it.


The total length of your hair's growth cycle determines the maximum length your hair can grow.


Q. Why doesn't my eyebrow hair grow as long as my head hair

A. The growing cycle of your hair as well as being genetically determined is different depending on where on your body the hair is located. The hairs in your eyebrows just have a shorter growing cycle than those on your head.


Scientists aren't completely sure why this is but natural selection probably has something to do with it: waist length eyebrow hair would have been a distinct disadvantage for our ancestors.


Q. How quickly does hair grow

A. The average rate is a centimetre a month.


Q. Will trimming my hair regularly make it grow past its maximum length

A. No, although it will help it reach its optimum length. Environmental stresses and chemical treatments do cause the hair shaft to split. So the longer you leave your hair the worse the spilt end, regular trimming will stop the split travelling further up the shaft.


But it won't help your hair grow any longer than the length it would grow anyway.


Q. How fast does my hair fall out

A. Hair is shed and replaced at around 40 to 100 hairs a day.


Want to know why your body does or doesn't do something Click here to ask a question.


by Lisa Cardy

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