I have been using this alpha hydroxy combination for at least 9years. I am mistaken for being anywhere from 5 to 10 years younger than I am. I have tried some of the retinol products as well as vitamin c, but keep coming back to this combo!. Daily with the 5% at night, and once a week with the 10% at night. There is a sting with the 10%, and I think there was a sting with the 5 % when I first started using. Don't be alarmed by seeing flaky dead skin on your face, this can be remedied. One of my tips for use with this or any other exfoliating product is that when you shower, and after using cleanser or soap, step out away from the water, and try manual fingertip exfoliation in small circles all over the face to help clear the dead skin. You feel little balls of the skin forming under your finger tips. Then after I feel I've gotten the most of the skin off, I rinse it away. This works great for me, but some of my friends use micro-fibre cloths to get the skin exfoliating.