If I stop shaving for two or three days, my face starts to itch.  The itching goes on for a few days, then stops.  Why?  What does my skin know or care about how long my whiskers are?

When I grow a beard, ginger and grey facial hairs start to appear amongst my usual dark coloured hairs, but only after about a week or so of growth.  Is this a case of the original hairs changing colour (or appearing to change colour) over time, or is there some reason why the ginger and grey coloured hairs appear to start growing at a later stage in the life of my beard?  Any suggestions gratefully received.

Each January I grow a beard (everyone should have a hobby). Each year my beard contains more grey.  This year I have noticed that the grey hairs grow faster than the non-grey hairs. Why?