Why does alcohol have antiseptic effect?

There are many types of alcohol, but generally only ethanol and isopropanol are used as disinfectants These two chemicals can effectively kill all kinds of bacteria, viruses, protozoa and fungi, and have relatively low toxicity to humans Alcohol is the most common disinfectant for skin It is often used as liniment or gel They are mainly used for surface treatment, but they are not generally used for disinfection The main effect of alcohol on microorganism is to coagulate basic protein, make it invalid, and lead to cell death or inhibit reproduction They also dehydrate and interfere with cell membrane function Proteins are common to all organisms and perform many essential functions in cells For example, proteins called enzymes allow cells to perform chemical reactions that keep them alive Protein molecules have complex shapes, which are very important for their own behavior If protein loses shape, it is difficult to function normally Protein shape loss, also known as denaturation, occurs when the bond that holds the shape breaks Denatured proteins tend to coagulate, meaning that molecules gather together to form an invisible entity Alcohol denaturates proteins by breaking down hydrogen bonds in different parts of the molecular chain, which link oppositely charged hydrogen and oxygen atoms They can do this because they form hydrogen bonds on their own in these places, leading to the loss of shape of protein molecules Their effectiveness depends on the concentration Ethanol, for example, works best against microbes at 70% concentration because it is easily absorbed by cells If the concentration is higher, it coagulates protein on the cell surface and blocks further penetration; although it is temporarily inactivated, the microorganism may still survive Although ethanol and isopropanol are similar fungicides, their resistance to different microorganisms is different Ethanol is better than isopropanol in virus resistance, but the opposite is true in bacteria resistance In addition to denatured proteins, these alcohols also dehydrate and can dissolve lipids such as fats and greases, which to a certain extent will cause damage to the cell membrane Ethanol has a better dehydration effect, and isopropanol has a greater impact on lipids Use alcohol is often used as hand sanitizer Hospital workers frequently wash their hands with Fungicides to prevent dangerous infections In addition to liquids and gels, alcohol and liniment and other forms of products Ethanol and isopropanol can be used for skin disinfection before operation Although these substances can cause skin dryness and mild irritation, normal use does not damage living tissues because they are protected by the outer layer of dead skin cells However, neither alcohol can be taken internally or used in sensitive body parts Except for occasional use in an emergency, alcohol is not generally used to disinfect wounds because it can damage internal tissues Other fungicides are sometimes mixed with alcohol to increase their potency A typical example is tincture iodine, a solution of iodine in alcohol Advantages and disadvantages as a bactericide, alcohol can play a role quickly, can effectively resist most harmful microorganisms and other benefits It evaporates quickly, so it won't leave the skin wet for too long But this in turn means that the potency lasts for a short time, and microorganisms can still survive on the surface shortly after the application of alcohol It is also for this reason that other bactericidal ingredients with longer retention time will be added In the environment where conditions are not suitable for reproduction, some bacteria can lurk in the form of spores for a period, and then reactivate after environmental improvement The spores are very tough Although alcohol can temporarily inactivate them, they usually cannot be killed In the same way, other ingredients can be added to enhance the efficacy of killing spores Ethanol and isopropanol have irritating and dehydrating effects on skin For this reason, commercial alcohol hand sanitizers are often added with moisturizing and moisturizing ingredients.