Re: combination skin
Nope. In the U.S., Retin A/Tretinoin requires a physicians prescription (I buy mine online). Many over-the-counter products contain retinol which is a derivative but the concentration is TINY. With products, ingredients are generally listed in order of importance/amount (can’t find the proper term lol). So even with products that claim they are retinol or whatever…..look at the actual ingredient list to see how far down the line its listed.
BTW, Retin A should NEVER be used during the day time! I don’t even get how its a good idea to use products with retinol/other acids during the daytime b/c I see so many creams that has it…..unless again the amount is to little that it really doesn’t matter. 
Vitamin C daytime with sunscreen. Anything containing retin-a OR any type of acids/peels etc. at night.