well im not sure about 20% yet coz personally mine is currently 10% and its by the ordinary brand. but im switching to 20% too from the one i got from indiamart once it runs out. so far it has been good no issues for me on 10% and i apply it in the morning everyday along with my vitamin c, hyaluronic acid and spf. so i guess best u can try the 20% out every other day first and observe if causes any issues or not.