Chills are your body’s way of generating heat through rapid, involuntary muscle contractions and relaxations. They can signal anything from a simple cold environment to a brewing infection, a hormonal shift, or even a powerful emotional experience. Most of the time, chills are harmless and temporary, but in certain contexts they point to something that needs attention.
How Your Body Produces Chills
A region at the front of your brain called the hypothalamus acts as your internal thermostat. When it senses that your body temperature is too low, or when it receives chemical signals during an infection that raise its target temperature, it kicks off a chain reaction. Nerve signals travel down through the brainstem and into the spinal cord, where they activate your skeletal muscles in a rapid, rhythmic pattern. That’s shivering. Each tiny contraction converts energy into heat, warming you from the inside.
This system also controls blood flow to your skin. When you get chills, blood vessels near the surface constrict to keep warm blood closer to your vital organs. That’s why your skin feels cold and may look pale or develop goosebumps even though your body is actively trying to raise its core temperature.
Why Chills Often Come Before a Fever
This is the cause that confuses most people: you feel freezing cold, but your temperature is actually climbing. During an infection, your immune system releases signaling molecules that reach the hypothalamus and essentially reset your thermostat to a higher setting. Your brain now treats your normal 98.6°F body temperature as “too cold,” so it triggers shivering and blood vessel constriction to close the gap. You feel chilled because, relative to the new target, you are cold. Once your core temperature reaches that higher set point, the shivering stops and you feel hot instead.
This is why chills often predict a coming fever. If you start shivering and feeling cold without an obvious environmental cause, there’s a good chance your temperature is on the way up.
Infections That Commonly Cause Chills
The most familiar culprit is the flu, but chills accompany a wide range of infections. On the viral side, common triggers include COVID-19, the common cold, RSV, mono, viral pneumonia, and gastroenteritis (stomach bugs). Bacterial infections that frequently cause chills include strep throat, urinary tract infections, bacterial pneumonia, sinus infections, and cellulitis (a skin infection).
Tick-borne illnesses like Lyme disease and Rocky Mountain spotted fever can also start with chills, as can foodborne infections from salmonella, E. coli, and listeria. In general, if an infection is strong enough to trigger a fever, chills are likely part of the package.
Non-Infection Causes
Not all chills mean you’re sick. Several other triggers can set off the same shivering response.
- Cold exposure: The most straightforward cause. Your body shivers to maintain its core temperature. Shivering typically starts when your core temperature drops below 95°F (35°C), which marks mild hypothermia. If your temperature falls below about 90°F (32°C), shivering actually decreases, and below 82°F (28°C) it stops entirely, which is a dangerous sign that the body’s warming mechanism has failed.
- Low thyroid function: An underactive thyroid slows your metabolism, reducing the heat your body naturally produces. Sensitivity to cold is one of the hallmark symptoms, and some people experience difficulty regulating body temperature in both directions.
- Low blood sugar: When blood glucose drops too low, your body releases stress hormones that can trigger shakiness and chills as part of the fight-or-flight response.
- Menopause: Over 80% of women going through menopause experience hot flashes, which often end with a wave of chills as the body overcorrects after a sudden surge of heat and sweating.
- Intense exercise: Working out hard, especially in cool weather, can cause chills afterward. Sweating lowers your skin temperature, and once you stop generating heat through movement, your body may shiver to compensate.
Emotional Chills Are Real
You’ve probably felt a shiver run down your spine during a powerful piece of music, a moving speech, or a scene in a film. This phenomenon has a name: frisson. Unlike temperature-related chills, frisson is an emotional response, a physical signature of peak emotional experience. Research from MIT’s Media Lab describes it as a “somatic marker,” a bodily sensation that coincides with a meaningful psychological moment, similar to how nausea accompanies disgust or a racing heart accompanies anxiety.
Frisson is linked to pleasure, a sense of meaning, increased empathy, and even stress relief. Not everyone experiences it with equal intensity, but it’s a well-documented example of how tightly physical sensation and emotion are intertwined.
When Chills Signal Something Serious
Most chills resolve on their own or with basic comfort measures. But in certain situations, they’re a red flag. Sepsis, the body’s extreme and life-threatening response to an infection, often includes shivering or feeling very cold alongside other warning signs: clammy or sweaty skin, confusion, extreme pain, a rapid heart rate, and shortness of breath. If chills come with any combination of these symptoms, it requires emergency medical care.
In young children, the stakes are higher because their immune systems are still developing. A fever of 100.4°F (38°C) or above in a baby younger than one month old warrants immediate evaluation. For infants between one and three months, a fever with chills still calls for a thorough medical assessment. Warning signs at any age include a rash with small red or purple spots, slow capillary refill (press a fingernail and it stays white for several seconds), labored breathing, or unusual sleepiness and difficulty waking.
Managing Chills at Home
If your chills are from cold exposure, the fix is simple: add layers, get to a warm space, and drink something hot. Tea, coffee, or hot chocolate all help raise your internal temperature. Wearing layers is better than one heavy garment because you can adjust as your body temperature shifts, preventing the sweat-then-chill cycle that makes things worse.
If chills are accompanying a fever, bundling up in blankets can feel comforting even though your temperature is elevated. The shivering phase is temporary. Once your fever peaks, you’ll likely switch to feeling hot and wanting to shed those layers. Staying hydrated matters more than anything else during a fever, since you lose fluid faster when your metabolic rate is elevated. Water, broth, and electrolyte drinks all help.
Chills tied to menopause, low blood sugar, or thyroid issues tend to improve when the underlying condition is managed. Keeping a record of when chills happen, how long they last, and what else you notice can help identify patterns and point toward the right cause.