Night sweats are a common and often disruptive symptom experienced by individuals who are reducing or stopping chronic heavy alcohol use, a condition known as Alcohol Use Disorder (AUD). These episodes of drenching perspiration that occur during sleep are a physical manifestation of the body struggling to regain its equilibrium after prolonged chemical suppression. Medically termed sleep hyperhidrosis, this symptom is a predictable part of the withdrawal process. Understanding the biological science behind these night sweats requires examining how alcohol alters the body’s thermal control and how the brain and body react when the substance is removed.
How Alcohol Affects the Body’s Thermostat
The immediate effect of consuming alcohol involves a significant disruption to the body’s ability to maintain a stable internal temperature, a process called thermoregulation. Alcohol acts as a potent peripheral vasodilator, causing the small blood vessels near the skin’s surface to widen. This dilation increases blood flow to the skin, which creates a temporary sensation of warmth and flushing.
However, this increased surface blood flow also accelerates heat loss to the environment. The body’s core temperature begins to drop as heat is rapidly diverted away from the internal organs. In response to this unintended cooling, the body’s internal thermostat attempts to compensate by activating its primary cooling mechanism: sweating.
This alcohol-induced sweating is an attempt to stabilize the system, but it often contributes to dehydration. The initial disruption to temperature control sets the stage for a rebound effect later, when the body’s systems overcorrect for the chronic chemical imbalance caused by heavy drinking.
The Core Mechanism: Autonomic Nervous System Hyperactivity
The most significant cause of night sweats during alcohol withdrawal is a state of hyperexcitability in the central nervous system (CNS), which manifests as Autonomic Nervous System (ANS) overdrive. The ANS controls all involuntary bodily functions, including heart rate, blood pressure, and sweating. Chronic alcohol use dramatically alters the balance of the brain’s two main chemical messengers.
Alcohol enhances Gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter, and suppresses glutamate, the main excitatory neurotransmitter. Over time, the brain attempts to compensate for this continuous chemical dampening by becoming less sensitive to GABA and ramping up glutamate production.
When alcohol is abruptly removed, the brain is left with an abundance of excitatory glutamate and a reduced ability to utilize inhibitory GABA. This creates a chemical imbalance known as a glutamate rebound. The resulting state of CNS hyperexcitability directly triggers the sympathetic nervous system, one branch of the ANS, into a state of hyperarousal.
The sympathetic nervous system is responsible for the body’s “fight or flight” response. This overdrive floods the body with signals that elevate heart rate, increase blood pressure, and activate sweat glands across the body. Night sweats are a direct physical manifestation of this heightened state, as the body attempts to dissipate the perceived internal heat generated by the nervous system’s activity.
Metabolic and Hormonal Contributors to Night Sweats
Beyond the nervous system, several metabolic and endocrine factors common in chronic alcohol users amplify the sweating response during withdrawal. Alcohol places a burden on the liver, the organ responsible for breaking down alcohol and regulating blood sugar. The process of metabolizing alcohol itself generates heat and increases the body’s overall metabolic rate.
The liver converts alcohol into acetaldehyde, which can further activate the sympathetic nervous system and raise body temperature. An impaired liver may also struggle to maintain stable glucose levels, leading to episodes of low blood sugar, or hypoglycemia. Hypoglycemia is a physical stressor that triggers the release of adrenaline, a hormone that causes profuse sweating.
Furthermore, chronic alcohol use disrupts the balance of several stress hormones, including cortisol and epinephrine (adrenaline). Withdrawal is a stressful event for the body, causing a surge in these stress hormones from the adrenal glands. These hormones are potent activators of the sweat response and intensify the sympathetic overdrive already initiated by the neurotransmitter imbalance.
The combined effect of metabolic heat generation, hypoglycemia-induced adrenaline release, and the persistent elevation of stress hormones contributes significantly to the severity and frequency of night sweats. These chemical and endocrine factors amplify the effects started by the hyperactive autonomic nervous system.