This method specifies the use of gas chromatography-mass spectrometry to determine the content of diethylene glycol (DEG) in cosmetic products. It is applicable to various product forms, including creams, emulsions, aqueous and oil-based liquids, gels, powders, and wax-based formulations. Currently, Safety and Technical Standards for Cosmetics only includes testing requirements for DEG in cosmetic ingredients, with no established method for finished products.