Chills: Causes and What They Mean

Evening, you're already under a blanket, and suddenly you start shaking: your shoulders tense up, your teeth chatter, even though the room is warm. Chills are not a disease but the body's way of warming up, and they can often help you understand what will happen next. Let's calmly, without panic, figure out what they mean and when it's time to see a doctor.

What chills are

Chills are a sensation of cold caused by spasm of the superficial, cutaneous blood vessels. They are accompanied by muscle trembling — primarily of the masticatory muscles, then the muscles of the shoulder girdle, back, and limbs — and by contraction of the arrector pili muscles, that very "goosebumps."

"Goosebumps" and chills are not the same thing: hairs stand up both from cold air and from strong emotions. And a feeling of chilliness in neuroses is a purely subjective sensation, without real trembling. With chills, heat loss decreases, heat production increases through muscle contractions, temperature rises, and the chills usually end.

Bottom line: chills are thermoregulation in action, not a separate diagnosis.

Why chills occur

The trigger is a deviation of temperature from the set point, about 37 degrees, about which the hypothalamus receives a signal from cold receptors in the skin or from internal receptors. During inflammation, prostaglandin E2 is produced, it binds to receptors in the hypothalamus, and the latter gives the command for thermogenesis. Muscles contract, energy goes toward warming — this is contractile thermogenesis.

It is triggered by hypothermia, the onset of fever in infections, injuries and other diseases, and certain medications. In a healthy person, chills are a normal protective reaction to cold; in easily excitable people, they are a reaction to excitement or fright.

Bottom line: there are many causes, but the mechanism is one — the body decides it is cold and starts warming up.

Chills with elevated temperature

Most often chills are associated with fever: they often herald a rise in temperature. A temperature of 38 °C and above is usually considered elevated, although normal varies from person to person and changes throughout the day.

The thermometer doesn't decide everything. If you have chills, you feel hot or cold, you are sweating, your skin is warm and red, your temperature may be elevated even at readings below 38 °C. Chills also occur at the height of fever, when the temperature fluctuates sharply.

Bottom line: look not only at the thermometer but also at how you feel.

Chills without fever: possible causes

Sometimes you feel chills but the thermometer reads normal. The causes are the same: hypothermia, reaction to medications, excitement or fright, neurotic chilliness. Sometimes chills come first and the temperature rises later.

In children, chills are common, and even a mild illness can cause a high temperature; infants usually do not have obvious chills. Chills are also a characteristic symptom of certain diseases, such as malaria.

Bottom line: chills without fever are not uncommon and by themselves do not indicate the severity of the condition.

Accompanying symptoms to pay attention to

Chills rarely come alone, and the company varies. Doctors are alerted by:

• neck stiffness, confusion, irritability, or lethargy;
• severe cough or shortness of breath;
• pain or burning in the abdomen;
• frequent urination.

Bottom line: you should look not at the chills but at what is happening alongside them.

When chills require seeing a doctor

Most episodes resolve on their own, but there are boundaries beyond which you should not wait. A temperature that does not come down or keeps rising is a reason to see a doctor. A fever that does not resolve within three days or lasts longer than five is also a reason.

In children the thresholds are stricter: a child under 3 months with a temperature of 38.3 °C or higher — see a doctor immediately; a child from 3 months to 2 years — if the temperature lasts longer than 24 hours; above 40 °C on several consecutive measurements — at any age.

At the appointment, the doctor will ask whether it is just a sensation of cold or real trembling, what the highest temperature was, whether the chills recur and how long an episode lasts. They will examine the skin, eyes, ears, nose, throat, neck, chest, and abdomen. Sometimes a complete blood count, urinalysis, blood, sputum, and urine cultures, and a chest X-ray are ordered.

Chills by themselves are not a reason to call an ambulance. Call 103 or 112 if, against a background of chills and high fever, confusion with marked lethargy, neck stiffness, or difficulty breathing appears.

Bottom line: the more fully you describe the picture, the more accurately the doctor will choose what to check.

This material is for reference and does not replace a doctor's consultation: if in doubt, call your doctor, who will figure it out together with you.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer