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Why 75% of alcohol sterilization is best, not 95% alcohol

Recently, for coronavirus, some experts pointed out that 75% of alcohol (ethanol) can effectively kill the virus, so everyone has snapped up medical alcohol for disinfection. Why is 75% alcohol effective for killing the virus? Would it be better to use 95% alcohol? What should be paid attention to in the process of using medical alcohol?

First, we must understand the type of alcohol, alcohol is divided into industrial alcohol and medical alcohol. At the time of purchase, the main components of alcohol can be viewed and distinguished. The main component of medical alcohol is ethanol, and the main component of industrial alcohol is methanol.

Industrial alcohol is the alcohol used in industry, also known as denatured alcohol, industrial fire wine. The methanol content is high. Due to different manufacturers, its proportion is not the same, generally more than 90%. It can be used in printing, electronics, hardware, spices, chemical synthesis, pharmaceutical synthesis, etc. It can also be used as a cleaning agent and solvent, but it cannot be used for human body disinfection. If industrial alcohol is used for skin disinfection, it may be partially absorbed by the skin, leading to poisoning.

Medical alcohol is a mixed solution of ethanol and water. Medical evidence shows that when the concentration of ethanol is 75%, the disinfection effect is the best. It can kill a variety of bacteria and viruses, and can also effectively kill new coronaviruses. Medical alcohol can be used for human body disinfection, the main purpose is disinfection and sterilization.

Different concentrations of medical alcohol have different effects.

  1. 25% ~ 50% of alcohol can be used for physical fever. Patients with high fever can wipe their body to achieve the purpose of cooling. Because wiping the skin with alcohol can dilate the blood vessels of the patient’s skin and increase the heat dissipation capacity of the skin, its volatility can also absorb and take away a lot of heat, so that the symptoms are relieved. But the alcohol concentration should not be too high, otherwise, it may irritate the skin and make the epidermis lose a lot of water.
  2. 40% to 50% alcohol can prevent bedsores. Prolonged pressure on the back, waist, and buttocks of long-term bedridden patients can cause bedsores. For example, pour a little 40% to 50% alcohol into the hands during the massage, and evenly massage the patient ’s compressed area to promote local blood circulation The purpose of the formation of bedsores.
  3. 70% to 75% alcohol can be used for sterilization and disinfection, including skin disinfection, medical device disinfection, and iodine deiodination. This refers to normal skin disinfection, not wound disinfection.
  4. 95% of alcohol is often used as a fuel for alcohol lamps and alcohol stoves by medical institutions. It is used to heat laboratory reagents or pharmaceutical preparations after ignition. It can also be used to temporarily sterilize small medical devices with its flame.

75% and 95% of medical alcohol are common in pharmacies. Is the higher the purity, the better the sterilization effect? Neither pure alcohol nor water is enough to denature the protein in the bacteria. Only when alcohol and water coexist, and at the same time relax the various attractive forces that maintain the geometric shape of the protein, the protein will lose its physiological activity. Therefore, only a certain concentration of alcohol solution can achieve good disinfection and sterilization purposes.

The 95% alcohol concentration is very high. An excessively high concentration of alcohol will form a protective film on the surface of the bacteria to prevent it from entering the bacteria and it is difficult to completely kill the bacteria. If the alcohol concentration is too low, although it can enter the bacteria, it cannot coagulate the protein in the body, nor can it completely kill the bacteria.

75% medical alcohol, because the water is mixed with alcohol, the concentration of alcohol becomes thinner. Dilute alcohol does not rush to solidify the protein on the surface of the bacteria but penetrates into the bacteria, and then solidifies the protein in the whole bacteria. So as to achieve the purpose of sterilization. When the alcohol concentration is 75%, its sterilization ability is the strongest.

Because alcohol is a flammable liquid, it is very inconvenient to carry. For personal travel, we recommend using 75% alcohol to disinfect wipes, which is very convenient.

What should be paid attention to when using alcohol?

Ethanol has strong volatility and is extremely flammable. When using alcohol, keep away from sources of ignition to prevent the ignition of alcohol and fire. Also, prevent burning and explosion caused by alcohol vapor. When spray disinfection is carried out in many places recently, alcohol vapor is easy to generate due to its strong volatility. Especially in closed spaces, such as rooms with closed doors and windows, alcohol vapor may accumulate and reach the explosion range. Burn or even explode.