What Causes Red Mark Between Eyes?

Hi, I have had a red mark that appears in between my eyes that comes and goes. It can't be a mark from glasses because i don't wear glasses. It isn't raised at all like a pimple or blemish, it looks like the vessels may be broken underneath the skin. I'm wondering if it may be heat related because I often notice it after i get out of the shower. It's been happening for years now and I'd like to get rid of it. Any ideas on what it could be?