"I had severe acne on my back which resulted in severe post-inflammatory hyperpigmentation (dark spots) all over my back. I have been using this product for several months (4-5 months) and my back is almost completely clear, enough that I'm not embarrassed to wear a tank top anymore. Hopefully I will be able to achieve completely clear skin on my back with longer use.I have suffered with this for over 15 years, have been to many dermatologist, spent a lot of money, and many many medications including Accutane, and this is the only product that has worked to clear the spots and is affordable especially for a large area as the back. I am very grateful. I do use this product on a daily basis. My skin can take it. Yes it does sting in the beginning but your skin will acclimate to it with time. It doesn't cause me any irritation, my skin is soft and acne free."