Alcohol intolerance is a condition where the body cannot properly metabolize alcohol, leading to unpleasant reactions after consuming even small amounts. Symptoms may include flushing, nausea, headaches, and rapid heartbeat. This intolerance is often due to a deficiency in the enzyme aldehyde dehydrogenase, which is responsible for breaking down acetaldehyde, a toxic byproduct of alcohol metabolism. People with alcohol intolerance may experience these symptoms regardless of the type of alcoholic beverage consumed. It is important to differentiate alcohol intolerance from alcohol use disorder, as the former is a physiological reaction, while the latter involves a psychological dependence on alcohol.