Methyl Phenol can denature proteins, so it has bactericidal effect. It has strong antibacterial activity against many microorganisms, such as gram-positive bacteria, gram-negative bacteria, mycobacteria, some fungi and viruses, and is resistant to Mycobacterium tuberculosis, spores and acid. The killing power of bacteria is poor. Phenol has the strongest activity in acidic solution; increasing temperature can also improve its antibacterial activity; the presence of organic matter will make its activity disappear. Diluted solution of Methyl Phenol can be used as a disinfectant and antiseptic, and has been used in surgery. In the 19th century, although the British doctor Lister had superb surgical techniques, he could not solve the problem of death of patients due to infection after surgery, and the mortality rate was 5%. He managed to find a drug to kill the microbes that infect the wound. Once he found that a cleaner used carbolic acid to eliminate the odor of the sewer, which inspired him to use carbolic acid dilute solution for surgery for the first time. The patients treated in this way did not experience any accidents such as infection. The incident shocked the world. In 1876, he completed a dissertation on disinfection, and only 10 years after it was published, the disinfection method was fully applied all over the world. Methyl Phenol is mainly used as an antibacterial preservative in injection and topical preparation products. The effective concentration is 0.1% to 0.5%, which can inhibit the growth of general bacteria. Cocci require a concentration of 3%, and to kill mold requires a concentration of more than 1.3%. Spores and viruses are very resistant to this product, so it is generally ineffective. Usually 1% to 5% concentration is used for disinfection of houses, poultry (livestock) houses, venues and other environments, and 3% to 5% concentration is used for utensils and equipment disinfection. The application method is spraying or soaking. The utensils and instruments should be soaked and disinfected for more than 30 to 40 minutes, but the troughs and drinking fountains can be used after soaking and disinfecting with normal water. Phenol is highly corrosive and toxic, mainly acting on the central nervous system, and the lethal dose for adults is about 1g. It has irritating, anesthetic and necrotic effects on skin and mucous membranes. Phenol is toxic by skin contact, swallowing or inhalation; mistakenly ingesting a small amount of Methyl Phenol can cause nausea, vomiting, shock, coma, and even death due to respiratory failure. The amount of phenol used as a preservative is small, so there are fewer adverse reactions. Since phenol is corrosive and irritating to tissues, it has been replaced by more effective and less toxic phenol derivatives, but the carbolic acid coefficient can still be used to express the bactericidal strength. For example, the carbolic acid coefficient of Methyl Phenol is 1, and when the carbolic acid coefficient of cresol to typhoid bacteria is 2, it means that the bactericidal ability of cresol is twice that of Methyl Phenol.