The redness of the skin after drinking is due to the lack of an enzyme in the body that helps metabolize ethanol, namely acetaldehyde dehydrogenase. 95% of the alcohol consumed in the body has to be metabolized by the liver, and the metabolic process depends on ethanol dehydrogenase and acetaldehyde dehydrogenase, and if these two enzymes have sufficient activity in the body, they can quickly break down alcohol into non-toxic and harmless carbon dioxide and water. If there is a lack of acetaldehyde dehydrogenase in the body, the acetaldehyde produced by the decomposition of ethanol cannot be decomposed by acetaldehyde dehydrogenase and accumulates in the body, causing the blood vessels to dilate and the patient’s skin to become red all over, especially the face. Acetaldehyde is a harmful substance that accumulates in the body and can damage the body’s organs, destroy DNA and even cause cancer. If your skin becomes red after drinking alcohol, you should not drink alcohol in the future.