I guess I must be the most vain person to answer your question so far because I do use makeup every single day and have since I was allowed to at age fourteen. I don't leave my house - even my bedroom - without it! I wish this wasn't true, but it is. I have very light skin and eye color and tend to just disappear without it. I don't recognize my own reflection until I at least get some eyeliner pencil on.
Having said that, if you are comfortable and happy with your appearance without makeup I wouldn't be too worried about using it. In fact, I am envious of you! I wish I could go back in time and alter my own notions about it, but it's too late for me now. I genuinely believe that makeup does improve my appearance and don't feel right without it. Judging by all the products available, I believe that many other women have fallen into the same trap.
I think that makeup is generally safe. In forty years of wearing it I have never had an eye infection or skin rash or any other issue. Like everyone has said, I do think that proper cleaning of your face is important. Also, NEVER share makeup with anyone or use old makeup, as it may have "spoiled" and grown bacteria or some such thing. If you try it and don't like it, it does wash right off.