QotW: Do hairs grow grey or turn grey?
Do hairs grow out grey, or do hairs that had colour eventually turn grey?
Katie Haylor finds out for listener Elizabeth why, when it comes to colour, it’s a question of 'hair today, gone tomorrow', with hair expert Desmond Tobin from University College Dublin...
Katie - Interesting question. Forum user Halc said that his grandmother's hair turned white in a week when her oldest son was killed in WWII, and user Evan_au said that genetic factors (eg age) and environmental factors (eg stress) affect the colour and darkness of the colour, and determine when the colour turns off, and how quickly the colour turns off in a given hair follicle.
To get to the root of the question, we spoke to hair expert Desmond Tobin, director of the Charles Institute for Dermatology at University College Dublin.
Desmond - Hair greying is associated with the aging process and is characterised by growth of hair lacking colouration within the hair follicle - a little ring of stem cells embedded in your skin that makes the hair. Under normal conditions, the colour-making cells in the hair follicle actively produce and transfer their natural hair dye, melanin, to keratin-producing cells that make up the bulk of the hair strand during this growth part of the life cycle. The result? Fully coloured hair - be it blonde, brown, black or red.
presenter - But, as some of us may well have experienced, hair doesn’t stay colourful for ever! Why?
Desmond - After between 5 and 8 rounds of the hair follicle life cycle (which each last up to 5 years), parts of hairs’ colouration machinery slow down, which results in either not as much colouration (so grey hair) or no colouration (white hair). And it's not just age, there is now good scientific evidence that psychosocial stress can affect many aspects of hair growth, including hair graying.
So Elizabeth, as you look at hair, you’ll see it either as “regrowing” or growing in a different colour to the others on the head, even from the same hair follicle. You might see, for instance, a black hair tip becoming grey-ish in the middle, even to white at the scalp.
Having said that, it is much easier to spot the fully white hairs against a dark background, and we do not know the ratio of fully white versus gradual greying hairs on the average scalp.