Andrew Steer, Cambridge asked:
Why do eyebrows start to grow out of control in old people? I was at the barbers last weekend, and after cutting his hair, the barber asked the elderly gentleman in front of me if he wanted his eyebrows trimmed (they did need it!).
We put this question to Des Tobin, Professor of Cell Biology, University of Bradford:
Hair growth is very susceptible to hormones, to the so-called sex steroid hormones: principally oestrogens and androgens. The dominant hormone for males is in the androgen category, particularly testosterone. Surprisingly the levels of testosterone continue to increase with age up until the age of 70. Since most of male hair is responsive to androgens with age and with increasing hormone levels you tend to get more and more vigorous hair growth particularly in the areas that were perhaps not as robust as when the individual was younger. For example, on the nose, ears and on their eyebrows. The nose and the ears have got thousands and thousands of hairs. They’re so small you can’t see – in fact the tip of the nose is the hairiest part of the body in terms of density of hairs per unit area. With time these can be stimulated with these male hormones which go up with age and therefore can become more cosmetically visible with age. The same applies for the eyebrows and for the ears. In women their oestrogen levels drop after menopause and their lower levels of testosterone become more engaged with the process of hair growth because they stimulate whereas oestrogens tend to inhibit. You’re just releasing more stimulatory power from the androgens we have.
It's not just eyebrows though is it? Ear canals, previously glabrous, can become quite hirsute in the latter years, but mainly in men.
I have found that my hair has just re-located, moving from my head to my ears and nostrils Ray hinton, Thu, 9th Oct 2008
Hi all, this answer doesn't make much sense to me. It is well known that the testosteron level in elderly men is in decline and that's why a lot of elderly men go on a testosterone replacement program. In fact elderly men usually have too much oestrogene and not enough testosterone, that's why their old fella shrinks amongst other things. Also if testosterone makes our hair grow stronger then why do we lose hair on our scalp? I'm not trying to be critical but I don't think the given answer is very clear. I mean why do we lose the hair in places we want to keep it and grow it in undesired ones? Harry, Sun, 28th Feb 2010