Vasodilation. Alcohol is a moderately potent vasodilator. As such, consumption of it can cause the capillaries near the skin to dilate, resulting in more blood flow to the skin and a flushed appearance. In addition, certain individuals can lack sufficient alcohol dehydronase, an enzyme that assists in the breakdown of alcohol. This is very common in asians.
acetaldehyde. Alcohol is metabolized into acetaldehyde, a chemical which causes marked flushing, sometimes with headache, skin itching and even fainting. The acetaldehyde is usually metabolized quickly into carbon dioxide and water, but some people do not have enough of the enzyme which causes this reaction. People of asian background, including native americans, especially have this problem, but others do too.