Facial redness: why do some people turn red after drinking alcohol?

The emergence of redness on the face after consuming alcohol is a sign of intolerance to this beverage. This phenomenon is usually accompanied by an acceleration of the heart rate, headaches, nausea, vomiting, dizziness, and a general feeling of physical discomfort. All these symptoms are likely to appear after the consumption of any alcoholic beverage, although they are more frequent when it has a high alcohol content. It's worth noting that what is commonly referred to as alcohol corresponds to ethanol, a molecule with the empirical formula C2H6O.

Following the ingestion of ethanol, the majority of its metabolism occurs in the liver. This process begins with a oxidation reaction controlled by the enzyme alcohol dehydrogenase (ADH), linked to NAD+, a cellular coenzyme. This enzyme facilitates the formation of acetaldehyde (C2H4O) from ethanol. A toxic product, acetaldehyde attacks cell membranes and disrupts the functioning of mitochondria. It is not only responsible for the state of intoxication but also for the appearance of redness on the face.

A high concentration of acetaldehyde in the human body leads to the release of histamine by mast cells, immune system cells. Histamine is a chemical mediator that acts by binding to H1 receptors on the endothelial cells of blood vessels, causing vasodilation. This increase in capillary diameter in turn leads to an intensification in blood flow. These two factors are visually reflected by the appearance of redness on the face.

Not everyone is equal when it comes to the redness that accompanies alcohol consumption. Indeed, some individuals are prone to developing erythema after a drink, while others never blush. A recent study conducted with a large panel of 1475 men showed that only 527 of them, or 36%, exhibited redness after consuming alcohol. This study also revealed that the onset of facial redness was correlated with a higher risk of high blood pressure. Indeed, it appears that this risk increases after 4 drinks of alcohol per week for those prone to redness, while it increases after 8 drinks per week for those not affected by this issue.

Important : Even if you do not experience redness after consuming alcohol, the WHO recommends limiting yourself to two drinks per day and spacing out the days with alcohol. High blood pressure is just one of the risks associated with this beverage: cirrhosis, cognitive disorders, cancers...

Several scientists have investigated the reasons that explain why some people flush and others do not after consuming alcohol. It has been observed that ethnicity plays a certain role in this difference, with individuals possessing darker skin often being less prone to flushing than those of so-called Caucasian or Asian types. Furthermore, genetics appear to be involved.

Indeed, following the transformation of ethanol into acetaldehyde, the metabolism of alcohol typically continues with the conversion of acetaldehyde into acetic acid (C2H4O2) under the action of the enzyme acetaldehyde dehydrogenase (ALDH2). However, individuals prone to redness tend to have a mutation in the gene coding for ALDH2. More specifically, it would be a substitution of glutamine by a lysine residue at the active site, which results in the inactivation of the ALDH2 enzyme. The metabolism of ethanol is then impacted and an accumulation of acetaldehyde in the body occurs. As mentioned earlier, this molecule is the cause of redness. The mutation of the ALDH2 enzyme gene is currently the favoured explanation for why some people blush after consuming alcohol.

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• Thesis by Véronique LAFOREST BÉRARD. Alcohol Dependence: Toxic Metabolites of Ethanol and Neurotransmitters (1995).

• KOHNO S. & al. Acetaldehyde prompts histamine release from human airway mast cells, leading to bronchoconstriction. International Archives of Allergy and Immunology (2004).

• YOON S. J. & co. Correlations Between Alcohol Intake, Facial Reddening Reaction, and Metabolic Syndrome in Healthy Males. Annals of Epidemiology (2012).

• YOON S. J. & co. Hypertension Associated with Alcohol Consumption Based on the Facial Flushing Reaction to Drinking. Alcohol: Clinical & Experimental Research (2013).