When illness strikes, many people experience chills, often accompanied by shivering, even though their body temperature might be rising. Chills are a common response to infection. Far from being a malfunction, this chilling experience is a coordinated part of the body’s defense mechanism against illness.
How Your Body Regulates Temperature
The human body maintains a stable internal temperature, typically around 37°C (98.6°F), through a process called thermoregulation. The hypothalamus, located in the brain, acts as the body’s thermostat, constantly monitoring and adjusting temperature. It receives input from temperature sensors throughout the body and initiates responses to either generate or release heat.
To generate heat, the body increases metabolic activity and muscle contractions, such as shivering. Conversely, heat is lost through mechanisms like sweating, expanding blood vessels near the skin (vasodilation), and direct transfer to the environment. This balancing act ensures the body’s internal environment remains optimal for cellular function.
The Immune System’s Role in Fever
When an infection occurs, the immune system detects invading pathogens. Immune cells, particularly macrophages, then release signaling molecules called pyrogens, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α). These pyrogens travel through the bloodstream to the hypothalamus, the brain’s temperature control center.
Upon reaching the hypothalamus, pyrogens trigger the synthesis of prostaglandin E2 (PGE2), which “resets” the body’s temperature set point to a higher level. This elevated set point is a deliberate immune strategy, as many pathogens struggle to survive and reproduce at higher temperatures. Fever, therefore, is an active defense mechanism designed to create an unfavorable environment for microorganisms and enhance immune cell activity.
Why You Feel Cold Despite a Fever
The sensation of coldness during a fever arises because the body’s actual temperature is lower than the new, elevated set point established by the hypothalamus. To reach this higher target temperature, the body initiates heat-generating and heat-conserving responses. A prominent response is shivering, where muscles rapidly contract and relax to produce heat.
The body also reduces heat loss by constricting blood vessels close to the skin’s surface (vasoconstriction), which diverts warmer blood to the core and makes the skin feel cool. Piloerection, or goosebumps, also occurs as tiny muscles cause hairs to stand on end. These physiological changes create the feeling of coldness and chills as the body strives to achieve its new, higher fever temperature.
Managing the Sensation of Chills
When experiencing chills, several comfort measures can help alleviate discomfort. Resting allows the body to conserve energy and focus on recovery. Staying hydrated by drinking fluids like water, clear broths, or herbal teas is important, especially since fever can lead to fluid loss. Wearing light, breathable clothing and using layered blankets can help manage temperature fluctuations, making it easier to adjust if you feel too warm or too cold.
Lukewarm baths or cool compresses can provide relief by gradually lowering body temperature, but cold water should be avoided as it can induce further shivering. Over-the-counter fever-reducing medications, such as acetaminophen or ibuprofen, can help lower the body’s set point and reduce chills. Consult a healthcare professional for guidance.