Sweating is the body’s primary cooling mechanism, while feeling cold usually signals the body is conserving heat. The phenomenon of “cold sweats” seems contradictory, yet it demonstrates that temperature regulation can be overridden by other powerful physiological responses. This paradoxical reaction occurs when non-thermal triggers activate the nervous system, forcing cooling responses even if the core temperature is not elevated or the skin feels cold.
Understanding Normal Thermoregulation
The human body is designed to maintain a stable internal temperature, generally around 98.6°F (37°C), a process known as thermoregulation. This precise balance is controlled by the hypothalamus, a small structure in the brain that acts as the body’s thermostat. The hypothalamus monitors temperature inputs from both internal organs and temperature receptors in the skin.
When the core temperature rises, the hypothalamus initiates cooling responses. It causes vasodilation, which widens blood vessels near the skin’s surface to allow heat to radiate away. Simultaneously, it signals eccrine sweat glands to produce sweat, which cools the body as it evaporates. Conversely, when the core temperature falls, the hypothalamus triggers heat-conserving actions. Blood vessels constrict (vasoconstriction) to reduce blood flow to the skin and keep warm blood near the core. If this is not enough, the body begins shivering, a rapid muscle contraction that generates heat.
Physiological Mechanisms of Sweating While Feeling Cold
The simultaneous occurrence of sweating and feeling cold points to a situation where the body’s internal thermostat setting, or set point, is rapidly changing, or where a non-thermal stressor activates the sweat response. One common scenario is the “crisis” phase of an infection-related fever. During a fever, the hypothalamic set point is raised, causing the person to feel cold and shiver even though their core temperature is elevated.
When the infection begins to clear or medication takes effect, the hypothalamic set point suddenly drops back to normal. The body is now drastically “overheated” relative to this new, lower set point, triggering a rapid and massive sweat response called diaphoresis. During this phase, the person may feel chilled because the sweat evaporating from their skin is cooling them quickly, even though the internal temperature is still high.
Another mechanism involves the body’s reaction to a state of shock, such as from severe injury or internal bleeding. Shock is a life-threatening condition where the organs do not receive enough blood flow. To prioritize blood supply to vital organs, the body activates the sympathetic nervous system, leading to intense peripheral vasoconstriction.
This vasoconstriction drastically reduces blood flow to the skin, making the skin feel pale and cold to the touch. Despite the cold periphery, the intense sympathetic activation also stimulates sweat glands, resulting in the characteristic cold, clammy sweat. This is not a direct cooling effort, but a side effect of the extreme “fight-or-flight” response.
Non-Temperature Triggers for Cold Sweating
When sweating occurs without an external heat source or a fever, it is often a sign of the body reacting to a systemic imbalance or stress. Low blood sugar, or hypoglycemia, is a frequent cause of cold sweats. When blood glucose levels drop, the body perceives this as an emergency and releases stress hormones, primarily adrenaline (epinephrine).
This surge of adrenaline is a counter-regulatory response designed to raise blood sugar, but it also stimulates the sweat glands through the sympathetic nervous system, causing sweating and symptoms like shakiness and a rapid heart rate. Because this sweating is caused by a hormonal trigger rather than heat, the skin often feels cold and clammy.
Emotional responses like anxiety, fear, or intense stress can also trigger cold sweats. These emotions activate the body’s “fight-or-flight” mechanism, which is mediated by the sympathetic nervous system and the release of adrenaline and cortisol. This activation directly stimulates the sweat glands, particularly the apocrine glands in areas like the palms, soles, and underarms.
Hormonal fluctuations, such as those experienced during menopause, can also result in night sweats that lead to a cold sensation. The sudden drop in estrogen can disrupt the hypothalamus’s control over temperature, causing a hot flash followed by profuse sweating. As the sweat evaporates, the rapid cooling causes a chill.