Science Questions

Why do we get more nose hair as we get older?

Tue, 23rd Feb 2016

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Question

Jean Crossman asked:

As we get old why do hairs grow down our nostrils?

Answer

Kat put this question to Chris SmithNose Hair

Chris: - It isnít just confined to me.  Everybody gets more hairy as they get older and the reason for this is that the hair that you have on your body is actually sensitive to androgens (these are testosterone-like chemicals) and, as you go through life, your testosterone exposure of your hair follicles that grow hair increases and so, therefore, you are destined to become hairier as you get older because testosterone encourages those hair follicles to grow more hair. 

Kat - And is this both men and women as well?

Chris - Yes it is, and specifically what testosterone or testosterone-like chemicals does is it prolongs whatís called the anagen phase of hair.  Hair goes through three phases: it has an anagen phase when the hair grows; it has a catagen phase when the hairs stops growing - the hair follicle switches off, the hair falls out; and then it goes into a telogen phase which is itís resting phase for a little while and then it starts growing again back to the start. The testosterone-like signals prolong the anagen phase, and the anagen phase dictates how long the hairís got to grow for, so therefore, youíre going to get a longer hair if you make the anagen phase longer.  So you will have the same number of hairs on your body but you will make thicker, bigger, longer hairs in response to testosterone.  To come back to your question about women.  Women are vulnerable to this but they tend to be less vulnerable until the age of the menopause because at the age of the menopause, the level of oestrogen in the bloodstream falls down and oestrogen reverses the effect on the hair follicle of testosterone - it stops the hair follicle responding to testosterone.  So when the oestrogen level comes down a bit, the testosterone becomes - and women do have testosterone - it becomes more dominant and, as a result, you do see more hairs growing.  Nose, ears, other parts of your body as well.

Kat - And what should you do about it?  You know can you just pluck them out?

Chris - Very, very painful.  I donít know if youíve tried plucking nasal hair but some people say this is the strongest stimulus that you can succumb tooÖ

Kat - Guys round the table - is there nose plucking here guysÖ no.

Chris - It makes you cry really, really profoundly but yes, you can trim them.  Itís a myth - if you trim the hair it will grow back more.  No evidence for that whatsoever so you can comfortably clip and away and snip away at your nose and ear hair and you will do it with impunity -  youíll fine.

Kat - Ginny...

Ginny - Why does this only apply to nose hair and ear hair and basically and hair where you donít want it?  Why does the hair on your head, particularly for men, get thinner with age then?

Chris - It does with women as well.  And there is a conversion process of turning the testosterone in the bloodstream or in women, testosterone-like chemicals. It gets converted into dihydrotestosterone in the scalp and, for some reason, certain populations of the hair follicles on the scalp are sensitive and they die in response to the build-up of testosterone there or the exposure to testosterone.  And because the receptor that does this is on the X chromosome, and men have only one X chromosome, women have two.  If you have the variant of the gene that makes you susceptible to balding and youíre a man, you have that and nothing else so youíre destined to lose your hair in that male pattern.  With women, because you have two chances because there are two X chromosomes and you randomly use one or the other all over your body, then youíve actually got more chance that you wonít see a lose of hair and also the testosterone that was lower to start with.

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