The experience of feeling alternately chilled and overheated, often accompanied by drenching perspiration, is a common feature of illness. This phenomenon is a deliberate, coordinated action by your body to fight off infection. Sweating during sickness is a sign of your internal temperature regulation system, governed by the hypothalamus, actively working to manage a fever and return your core temperature to its normal, healthy set point.
The Body’s Thermostat: How Fever Starts
The initiation of a fever begins when the immune system detects an invading pathogen, such as a virus or bacteria. Immune cells then release signaling molecules called endogenous pyrogens, like cytokines, which travel through the bloodstream to the brain. These pyrogens signal the hypothalamus to raise the core temperature set point. The hypothalamus interprets the normal body temperature as too low relative to this new, elevated set point. To bridge this gap, the body initiates heat-generating and heat-conserving responses. Peripheral vasoconstriction, where blood vessels near the skin constrict, reduces heat loss to the environment. This heat conservation often triggers shivering or chills. Shivering involves rapid muscle contractions that generate additional heat, raising the body’s temperature until it reaches the new set point.
Sweating as the Cooling Mechanism
Sweating occurs during the resolution phase of a fever, signaling that the body is overcoming the infection or that a fever-reducing medication is taking effect. When the pyrogenic signal fades, the hypothalamus resets the temperature set point back to its normal, lower range. With the set point lowered, the current body temperature is considered too high, prompting the cooling mechanism. The body initiates vasodilation, causing blood vessels in the skin to widen and bring hot blood closer to the surface, allowing heat to radiate away. The primary mechanism for rapid cooling is the production of sweat. As the liquid sweat evaporates from the skin’s surface, it carries a significant amount of heat away from the body, a process called evaporative cooling. The presence of sweat is typically a positive indication that the fever is breaking.
Other Causes of Excessive Sweating While Ill
Not all excessive perspiration during illness is directly related to the breaking of a fever. Night sweats are a common secondary symptom of various infections, where the body’s inflammatory response remains active while a person sleeps.
The body’s stress response to being ill can also trigger sweating, independent of temperature. Fighting an infection releases stress hormones like cortisol, which stimulate the sweat glands.
Certain medications used to treat illness, such as some antibiotics or fever reducers, may have side effects that include increased perspiration. Additionally, physiological events like hypoglycemia, or low blood sugar, can cause sudden, clammy sweating as the body releases adrenaline in response to the drop in glucose.
Knowing When Sweating is a Concern
While sweating is usually a normal physiological process, maintaining hydration is paramount because significant fluid is lost through perspiration. Sweating accompanied by certain other symptoms warrants immediate medical attention. These warning signs include new or excessive sweating paired with:
- Confusion
- Chest pain
- Lightheadedness
- Shortness of breath
If drenching night sweats persist for several weeks after the primary illness has resolved, or if the sweating disrupts daily life, it is advisable to consult a healthcare provider.