Skin peels generally have high levels of active ingredients and to get the best results from your treatment prep is vital. If you have never used active products and you apply a peel the skin may become sensitive. By introducing the ingredients to your skin over a few weeks prior to peels the receptors are open and get used to the ingredients. When you apply the peel with similar ingredients (but at a higher level) the receptors will know what is happen and not freak out. This results in a better and safer treatment for you.