The common experience of feeling a sudden chill, shivering, or getting goosebumps after consuming alcohol is a confusing sensation. Many people initially feel a warm flush, which makes the later cold feeling seem counterintuitive. This shift from feeling warm to cold is not a sign of alcohol “warming you up” as folklore suggests. Instead, it results from distinct physiological changes that disrupt the body’s ability to maintain a stable internal temperature. These mechanisms collectively lead to a drop in core body temperature.
The Immediate Paradox: Feeling Warm While Losing Heat
The initial feeling of warmth after drinking is caused by peripheral vasodilation. Alcohol acts on the smooth muscles surrounding blood vessels, causing them to relax and widen, especially those near the skin surface and in extremities like the face, hands, and feet. This widening increases blood flow to the skin, delivering warm blood from the body’s core to the periphery.
This rush of warm blood to the skin creates the pleasant, flushed sensation often associated with a drink. However, the skin is in direct contact with the cooler ambient air. Bringing warm blood to the surface dramatically increases the rate of heat loss to the environment, causing rapid heat dissipation. This causes the core body temperature to begin dropping, even while the skin feels warm.
The body trades a temporary feeling of skin warmth for a significant reduction in its internal temperature. This rapid heat loss is the primary physical mechanism that sets the stage for the later sensation of coldness, chills, and shivering.
How Alcohol Disrupts the Body’s Central Thermostat
The body’s temperature is regulated by the hypothalamus, a small region in the brain that functions as the central thermostat. This area constantly monitors the temperature of the blood flowing through it. It initiates corrective actions, such as shivering to generate heat or sweating to release it, to maintain a specific temperature set-point. Alcohol, being a central nervous system depressant, interferes with the hypothalamus’s ability to accurately sense and respond to temperature changes.
Alcohol can influence the hypothalamus to lower its regulated temperature set-point. The brain begins to believe the body is at a comfortable temperature, even as the core temperature starts to fall due to vasodilation. Because the thermostat is effectively reset to a lower value, the brain is slow to initiate the crucial counter-measures necessary to preserve heat.
This impairment means that the body’s natural defenses, like vasoconstriction (narrowing blood vessels) and shivering, are delayed or suppressed. The body loses heat faster than it can produce it. The brain fails to trigger the appropriate response, leading to an uncontrolled drop in core temperature and the eventual onset of severe chills.
Contributing Factors: Low Blood Sugar and Dehydration
Two additional physiological mechanisms contribute to the cold sensation: alcohol-induced hypoglycemia and dehydration. The liver plays a dual role in detoxifying alcohol and maintaining stable blood glucose levels. When alcohol is consumed, the liver prioritizes metabolizing the alcohol over releasing stored glucose into the bloodstream, a process called gluconeogenesis. This prioritization can lead to a drop in blood sugar, or hypoglycemia. Low blood sugar can trigger symptoms that include chills, sweating, and feelings of weakness, which compound the cold sensation caused by temperature dysregulation. Furthermore, alcohol is a known diuretic, meaning it increases urine production by inhibiting the release of vasopressin, the anti-diuretic hormone.
Increased urination leads to a net loss of body fluid, causing dehydration. Dehydration reduces the overall volume of blood circulating in the body, which impairs the efficiency of the circulatory system. A less efficient circulation makes it more difficult for the body to distribute heat effectively, worsening the feeling of being cold.