2-Methyl-4-isothiazolin-3-one (abbreviated as MIT) is a highly effective, broad-spectrum biocide and preservative belonging to the isothiazolinone class. By disrupting microbial cell membranes and inhibiting the activity of metabolic enzymes, it powerfully suppresses the growth of bacteria, fungi, and algae. It is frequently used in combination with 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) in a 3:1 ratio, a blend commercially known as "Kathon." MIT is widely utilized in various applications, including cosmetics, shampoos, lotions, paints, water treatment systems, and industrial circulating water. Chinese regulations stipulate a maximum permissible concentration of 0.01% (100 ppm) for its use in cosmetic products. However, MIT is a known sensitizer and constitutes one of the primary triggers for contact dermatitis; at high concentrations, it can cause skin and eye irritation, while prolonged exposure may potentially lead to neurotoxicity and allergic reactions. Consequently, its use in leave-on cosmetic products requires particular caution.