Sweating when unwell is a common physiological response, indicating the body is actively working to restore balance and fight illness. While sometimes uncomfortable, sweating plays a part in the body’s self-regulatory processes.
The Body’s Internal Thermostat and Fever
When the body encounters invading pathogens, such as bacteria or viruses, the immune system initiates a defense mechanism, often leading to a fever. This involves the release of substances called pyrogens. These pyrogens can be either exogenous, coming from outside the body like bacterial toxins, or endogenous, produced by the body’s own immune cells, such as cytokines.
These pyrogens travel through the bloodstream to the brain, targeting the hypothalamus, which functions as the body’s thermostat. The hypothalamus then “resets” the body’s temperature set point to a higher level. To reach this new set point, the body activates heat-producing mechanisms, such as shivering, and inhibits heat-losing mechanisms, like reducing blood flow to the skin, causing a person to feel cold despite a rising internal temperature. This elevated temperature helps create an unfavorable environment for many pathogens, hindering their multiplication and supporting the immune system’s efforts to combat the infection.
Sweating: The Body’s Cooling Response
Once the body has maintained a sufficiently high temperature to aid in fighting off infection, or as the illness begins to subside, the hypothalamus lowers its temperature set point back to the normal range. At this stage, the body needs to shed the excess heat accumulated during the fever. This is when sweating becomes prominent.
Sweat glands, particularly eccrine glands, produce a watery fluid that is released onto the skin’s surface. As this sweat evaporates, it draws heat away from the skin, effectively cooling the blood flowing near the surface. This evaporative cooling mechanism helps to bring the core body temperature down, indicating that the fever is breaking and the body is returning to its normal thermal regulation. This process dissipates heat and prevents overheating.
Beyond Fever: Other Causes of Sweating When Sick
Not all sweating during illness is directly linked to fever or its resolution; other factors can also contribute. “Cold sweats” occur when a person feels chilly but is still perspiring. These are often a manifestation of the sympathetic nervous system’s “fight-or-flight” response, triggered by stress, anxiety, pain, or even conditions like low blood sugar or low blood pressure, rather than temperature regulation. The body releases adrenaline, which can stimulate sweat glands and increase heart rate.
Night sweats, characterized by excessive perspiration that soaks sleepwear and bedding, can also occur independently of a fever cycle. While a warm sleeping environment can be a simple cause, night sweats during illness might indicate persistent infections, hormonal fluctuations, or certain underlying health conditions. Additionally, some medications taken for illness, including certain antidepressants, pain relievers, and antibiotics, can have excessive sweating as a side effect.
When to Seek Medical Advice
While sweating when sick is often a sign of the body’s normal healing processes, certain symptoms accompanying it warrant medical attention. Seek immediate care if sweating is accompanied by severe symptoms like difficulty breathing, chest pain, or confusion. These could indicate a more serious underlying condition.
It is also advisable to consult a healthcare provider if sweating leads to signs of dehydration, such as dizziness, reduced urination, or a dry mouth. Persistent or unexplained night sweats, especially if accompanied by other symptoms like unexplained weight loss or fever, should also be evaluated. For infants or young children, any elevated temperature should prompt a call to their pediatrician.