Although I have (oily) acne-prone skin and have never been fully pimple or acne-scar free, I can never seem to be able to describe how products have helped me like some people can. I've been using Cosrx's BHA liquid for a while now, and recently bought the AHA. The first time I used the AHA it gave me a tingling sensation, but the next time I used it again I did not have the same tingling sensation. I would say that the product does seem like it has been helping with my skin, but I would say be careful if your skin is sensitive.