What could it be? i have a red spot on my bottom lip, no pain, no blister.

Tough to say: Diagnosing "spots" is best done by a good history and physical examination. Factors such as age of pt, size of the spot, duration of the spot, precipitating events, possible allergens that may have caused the spot, etc. Are all things that go into a proper diagnosis. I would see your dr. Or a dermatologist (skin specialist) to get a definative diagnosis. Good luck.