The validation of cleaning is a key tool to ensure the quality of the final product, according to Good Manufacturing Practices. It allows to detect contamination risks and cross contamination. In this paper, by means of the risk study of the 18 semi-solid products manufactured using 21 different active principles, critical active ingredients used are selected and the acceptable superficial limit of them is calculated. The dosage unit of a semi-solid product is not clearly defined as in tablets. In this study, the fingertip unit (FTU) is used, knowing the amount of active ingredients contained in an FTU and the amount of FTU needed to cover the affected area, the amount of active ingredient per application is determined and the limit is calculated. The critical active ingredients selected were octyl salicylate, Limit = 0.0690 mg/mL and Nitroglycerin, Limit = 0.0002 mg/mL.