The corners of my mouth are cracking up

1) Hi Alice,

Just wanted to know if you knew what the little sores were that come right in the corner of your mouth on the outside, not inside. I've heard they are caused by something lacking in your diet. Right now I have two, one on each side, and I have no idea what has changed in my diet to cause them. Is there anyway to clear them up?

Thanks,
Dana

2) Alice,

My friend has been experiencing cracked skin at the corners of her mouth for about a week now. I seem to remember my mother having the same thing, and that the cause was a deficiency or reaction of some kind. What could be the cause and does it have a name? She would like to do some self-educating before going to see her doctor.

Thanks,
sd