All cosmetic products must be safe, especially those intended for babies and small children. Besides national guidelines and regulations, cosmetic products in the European Union are regulated by the EU Cosmetic Products Regulation. It pays particular attention to protecting the health of vulnerable population groups and recommends a specific assessment for cosmetic products intended for use on children under the age of three years. Nevertheless, standard procedures for the evaluation of the local tolerance are not given. Due to practical and ethical reasons clinical studies on adults should be a first step of compatibility testing. To consider physiological differences notably a not yet fully developed barrier function during the first years of life, barrier function of adult skin can be intentionally compromised by gentle experimental standardized procedures prior product application. As an alternative and depending on the objective target, only pre-screened sensitive subjects are included in the investigation. After extensive pre-examination and testing in adults, tolerance and performance of the final product can also be confirmed with non-incriminating observational studies under normal in-use conditions in children under physician control.