Question: when your old why does your hair change colour

Pip Millington answered on 14 Nov 2016:

This is a pretty difficult question to answer but it probably has something to do with your genetics and how that interacts with the environment.

You get pigment in yours skin and hair from the production of a pigment called melanin which is produced in cells called melanocytes. If these are associated with fair follicles that your hair contains some of this pigment. Mouse studies has shown that mice without a gene (part of the DNA code) called Bcl2 get white hair early on in life so this gene is probably important in regulating hair colour. There are other genes which have a similar function.

However, about 70% of going grey is due to the environment. The environment comes into play because at some point, there are either fewer melanocytes or melanin is not produced so much. The environment probably causes changes in the cells which affect how much those particular genes are used. We know that DNA can be altered by a process called methylation which means that extra atoms get stuck to it which alter how much the code gets read by the cell. It might be that this process is involved but no-one really knows for sure.