Facial flushing after alcohol consumption, often experienced as redness in the cheeks, is primarily a physiological response linked to how the body metabolizes alcohol. The liver breaks down alcohol into acetaldehyde, a toxic compound. Under normal circumstances, acetaldehyde is quickly converted into acetate, a less harmful substance. However, some individuals, particularly those of East Asian descent, have a genetic variation that impairs the enzyme responsible for this second step, leading to an accumulation of acetaldehyde.
The accumulation of acetaldehyde causes several physiological effects, including the dilation of blood vessels, especially in the face. This dilation is the direct cause of the visible redness. While generally harmless, this reaction can be an indicator of an increased risk of certain health problems associated with long-term alcohol consumption, most notably esophageal cancer in individuals with the genetic variation. Historically, the physiological response has been associated with cultural stigmas and perceptions of alcohol intolerance.