Each winter I let my whiskers grow out. There is a reason for this. A great deal of blood goes to your head to feed the brain. Approximately 60% of your body heat is lost thru your head. There is an old say "If your feet are cold, put on a hat." For me I could probably get my with less blood going to the head as I have little up there to take care off. In 1993 I severly frostbit my feet and hands. The result was both my feet were amputated thru the metatarsal and the heels had to be rebuilt. Now my "goofy" feet are very sensitive to the cold. My hands came out okay but are still sensitive to the cold. So I grow a beard in winter to help keep my feet and hands warm. People ask me why my beard is white and my hair is brown. I tell them that the top of my head is higher from the ground and is covered with a hat and being higher is not affected by the air polluation. Actually my hair is going grey but it still looks darker.