The first big mistake people make is thinking that higher strength acids will work better or faster, and so book in for chemical peels or buy clinical strength acids online . "Too much of a good thing can cause a problem," says Adarsh Vijay Mudgil, MD, founder of Mudgil Dermatology in NYC. "When too much acid (either too strong, too frequently applied, or left on for too long) is used, the skin can essentially get mildly burned. This can cause pigment to drop into the dermis (the layer of skin just under the outer surface) and result in hyperpigmentation." Dr Craythorne adds: "With very strong acids, what you’re doing is creating even more inflammation. This then drags some of the pigment and melanocytes deeper in to the skin." This means pigmentation becomes more difficult to fade.