actually the PTR retinol fusion pm is a 1.5%. There is no limit that it can have in a product because it is not regulated my the FDA and it is not as strong as its prescription cousins of retinoids.
I use the ptr 1.5% retinol every night with zero irritation even from the very first night of appication on. i was able to start using it daily with no redness or peeling issues. and this is comming from someone who could NEVER use a retinol because i would get sick of the constant irritation. either try the PTR retinol or Miracle Worker pads from Philosophy.