The answer is 20 years old.  I bet you were shocked at that.  I know I was when I first heard that.  Every year we lose 1% of our collagen.  When you get to be 40 you should be well on your way to a good skincare routine.  If you would like more info on how to have a good skincare routine and balance call for a free consult anytime.  519-542-0079  We are always happy to help.