It is not true that the higher the concentration of alcohol, the better the disinfection effect. In medicine, alcohol is often used to disinfect skin or wounds, and many people think that the higher the concentration of alcohol, the stronger the germicidal effect. In fact, the sterilization effect of alcohol is not stronger with higher concentration, there is a certain range of effective sterilization concentration, too high or too low concentration does not play a sterilization role. The surface of the bacterial body has a layer of envelope, the main component is protein. In a certain concentration of aqueous solution, alcohol can penetrate into the body of the bacteria, causing coagulation and denaturation of bacterial proteins, thus killing the bacteria. The concentration of alcohol used for disinfection in medicine is often formulated to 75% or 70%. If the concentration of alcohol is too low (below 70%), although it can also penetrate into the bacteria, the coagulation effect on bacterial proteins is weak and does not achieve the purpose of sterilization. If the alcohol concentration is too high, causing protein dehydration coagulation is too strong, when it comes into contact with bacteria, it can quickly lead to protein coagulation denaturation on the bacterial envelope. At this point, the surface of the bacteria in turn formed a protective layer to prevent the alcohol to the bacteria continue to penetrate the body, the proteins in the body of the bacteria do not come into direct contact with alcohol, and vitality will not disappear. Once the alcohol evaporates, the cells within the envelope may break through the envelope to revive and reproduce, so that the alcohol will not play a role in sterilization. In addition, even an effective concentration of alcohol only kills bacteria, not bud cells or viruses. When skin disinfection is performed clinically before surgery, the skin is often coated with iodine, which is more effective, and then deiodized with alcohol to avoid the irritation of iodine to achieve a better sterilization effect.