I don't think you can help it really. It's a natural physiological reaction to feeling embarrased or talking to someone you like. I think what is best is to accept it. It can be quite cute actually. You can even joke about it "Look, you made me all red" while smiling or laughing.
If the other person tries to belittle you for that, then they got some major problems. My face going red and wide grins have become a natural part of how I interact with my friends now. I just laugh at it - it tends to put a smile on their face as well.