page_title: Alcohol flush reaction
section_title: Genetics
hierarchical_section_title: Alcohol flush reaction / Causes / Genetics
caption_attribution_description: English: Genetype frequency of ALDH2 polymorphism, rs671, which affects alcohol flush reaction.
context_page_description: Alcohol flush reaction is a condition in which a person develops flushes or blotches associated with erythema on the face, neck, shoulders, and in some cases, the entire body after consuming alcoholic beverages. The reaction is the result of an accumulation of acetaldehyde, a metabolic byproduct of the catabolic metabolism of alcohol, and is caused by an aldehyde dehydrogenase 2 deficiency.
  This syndrome has been associated with lower than average rates of alcoholism, possibly due to its association with adverse effects after drinking alcohol. However, it has also been associated with an increased risk of esophageal cancer in those who do drink.
  Approximately 30 to 50% of East Asians show characteristic physiological responses to drinking alcohol that includes facial flushing, nausea, headaches and a fast heart rate.
context_section_description: Alcohol flush reaction is best known as a condition that is experienced by people of East Asian descent. According to the analysis by HapMap project, the rs671 (ALDH2*2) allele of the ALDH2 responsible for the flush reaction is rare among Europeans and Sub-Saharan Africans. 30% to 50% of people of Chinese, Japanese, and Korean ancestry have at least one ALDH2*2 allele. The rs671 form of ALDH2, which accounts for most incidents of alcohol flush reaction worldwide, is native to East Asia and most common in southeastern China. It most likely originated among Han Chinese in central China. Another analysis correlates the rise and spread of rice cultivation in South China with the spread of the allele. The reasons for this positive selection are not known, but it has been hypothesized that elevated concentrations of acetaldehyde may have conferred protection against certain parasitic infections, such as Entamoeba histolytica.
caption: Genotype frequency distribution of ALDH2 (rs671).
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