Skin reacts differently from one person to another. By nature, it can be more or less receptive to ingredients. Also, depending on many health or environmental factors, the effectiveness of a product can be slowed down. Nevertheless, cell renewal - which occurs at the same rate for everyone - is the fundamental element to take into consideration when using a cosmetic product or a shampoo. It is necessary to wait several weeks (3 to 6) in order to notice the true effects of a product. Depending on your receptivity to a formula's active ingredients, noticeable results may be visible after 2 cell renewals, i.e. after 6 weeks.