Most metal-cutting operations require the use of cutting or metalworking fluids for cooling and lubricating, for the removal of fine metal particles (metal chips), and to maintain overall cutting quality of the workpiece and extend tool life. Cutting fluids are commercialized and complex mixtures of several chemicals: a base oil, additives, and de novo substances that develop (or are added) during use. The most common diseases caused by cutting fluids are skin diseases, particularly irritant but also allergic contact dermatitis; problems of the respiratory tract (e.g., occupational asthma) and other disorders occur less frequently. The main responsible sensitizers are additives, such as alkanolamines (especially monoethanolamine), colophonium (rosin, and its component abietic acid), formaldehyde (releasers), and isothiazolinones. Other skin disorders like squamous cell carcinoma, follicular diseases (e.g., folliculitis, oil acne), pigmentation disorders, granulomas, and infections are rarely observed nowadays due to optimized formulations of metalworking fluids and better working conditions.