Increased sweating is a common physiological response when the body is unwell. This physiological response is often a natural way the body manages its internal environment during an illness.
The Body’s Fever Process
When an infection enters the body, the immune system initiates a complex defense. Immune cells, like macrophages and monocytes, recognize foreign invaders such as bacteria or viruses. These cells then release signaling molecules called pyrogens. Pyrogens can be either exogenous (from the pathogen itself) or endogenous (produced by the body’s immune cells).
These endogenous pyrogens, including cytokines, travel through the bloodstream to the brain. They particularly target the preoptic area of the hypothalamus, a region often referred to as the body’s thermostat. Upon receiving these signals, the hypothalamus raises the body’s temperature set point.
This means the body now perceives its normal temperature as too low, initiating mechanisms to increase heat production and conserve heat. The body responds by shivering, a rapid muscle contraction that generates heat, and by constricting blood vessels in the skin, which reduces heat loss to the environment. These actions collectively work to elevate the core body temperature to the new, higher set point, resulting in a fever.
Sweating’s Role in Cooling
Once the immune system has effectively combated the infection, or when fever-reducing medications begin to take effect, the pyrogenic signals diminish. This allows the hypothalamus to reset the body’s temperature set point back to its normal range. The body then recognizes that its current elevated temperature is now above the desired set point. To bring the temperature down, the hypothalamus activates cooling mechanisms.
One primary cooling mechanism is vasodilation, where blood vessels in the skin widen to increase blood flow to the surface. This allows more heat to dissipate through the skin. Simultaneously, the body activates its sweat glands, which produce sweat. As sweat evaporates from the skin’s surface, it carries heat away from the body in a process known as evaporative cooling. This efficient heat transfer helps to lower the core body temperature back to the normal set point.
Other Contributors to Sweating
Beyond the direct process of fever resolution, several other factors can contribute to increased sweating during illness. Dehydration, a common issue when sick due to fluid loss from vomiting, diarrhea, or reduced intake, can sometimes paradoxically lead to more sweating as the body struggles to regulate temperature with insufficient fluid. The general stress response of the body to illness can also trigger the sympathetic nervous system, leading to increased activity of sweat glands.
Certain medications taken to alleviate symptoms of illness may also induce sweating. For instance, some pain relievers, like acetaminophen, work by reducing fever, and the subsequent cooling process can involve sweating. Decongestants, which can stimulate the nervous system, may also increase sweat production as a side effect. Anxiety related to being unwell, or even the discomfort of symptoms like nausea or pain, can also activate physiological responses that include sweating.