I've been using tretinoin for a month ... and my face became redness ... is it normal?

Yes: If your face gets too red from using tretinoin, there are some things you can do to help. 1. Wait 20-30 minutes after you wash your face, before applying it. 2. Use a spot the size of a pea to cover your entire face. 3. Wash it off in the morning. 4. If it is too irritating when you use it daily, then you can use it 2-3 times a week, instead.