The most common reason is that the ethanol in alcohol is rapidly absorbed by the esophagus and stomach, and then converted into acetaldehyde under the action of ethanol dehydrogenase in the liver, which is a substance that causes the capillaries around the body to expand rapidly and is toxic and harmful, especially the capillaries on the forehead and face to expand significantly, thus causing redness after drinking. 2. The alcohol will be rapidly converted into acetaldehyde, which will cause the blush after drinking to be particularly intense and strong. 3. Drinking alcohol will also make the heart beat faster, blood pressure rise, and sympathetic nerves overexcited, which will also lead to abnormal congestion and expansion of capillaries, which will aggravate the blush after drinking.