Experiencing chills and feeling cold when your body temperature is actually rising is a common symptom of fever. This seemingly contradictory sensation is a normal part of your body’s defense system. Understanding the biological processes at play can help clarify why you might shiver and feel cold even when you have a fever.
Understanding Your Body’s Thermostat
Your body maintains a stable internal temperature through a complex regulatory system, controlled by the hypothalamus in your brain. This area functions like your body’s thermostat, setting a “set point,” typically around 98.6°F (37°C). When you develop a fever, this set point is deliberately raised by the hypothalamus, sometimes to 102°F (38.9°C) or higher.
With the new, higher set point, your body perceives its current temperature as too low, even if it is already above normal. To bridge this gap, the hypothalamus triggers mechanisms to increase and conserve heat. This includes vasoconstriction, where blood vessels in your skin narrow to reduce heat loss to the environment, and shivering, which involves rapid muscle contractions to generate heat. These responses cause the sensation of coldness and chills despite an elevated core body temperature.
How Your Immune System Triggers Fever
The immune system initiates a fever when it detects foreign invaders like bacteria or viruses. In response to infection, immune cells like macrophages release signaling molecules called pyrogens. These pyrogens, which can be either external substances from microorganisms or internal substances produced by the body, travel through the bloodstream to the brain.
Upon reaching the hypothalamus, pyrogens signal it to increase the body’s temperature set point. Pyrogens stimulate the production of prostaglandins within the hypothalamus. These then act on specialized neurons, effectively “tricking” the hypothalamus into believing the body is colder than it actually is, leading to the activation of heat-generating and heat-conserving responses that result in fever.
What to Do When You Have a Fever and Chills
When experiencing a fever with chills, focusing on comfort and supporting your body’s natural defenses is helpful. Staying well-hydrated by drinking plenty of clear fluids. Resting adequately allows your body to conserve energy for fighting the infection. Dressing in layers can help manage the fluctuating sensations of cold and warmth, allowing you to adjust as your body temperature changes.
While fevers are a beneficial part of the immune response, consult a healthcare professional if your fever is very high, consistently above 103°F (39.4°C) for adults, or lasts longer than three days. Seek medical attention promptly if you experience concerning symptoms such as a stiff neck, confusion, severe headache, shortness of breath, or severe abdominal pain.