Chills is a feeling of coldness occurring during a high

fever Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...

, but sometimes is also a common

symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...

which occurs alone in specific people. It occurs during fever due to the release of

cytokine Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...

s and

prostaglandin The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are derive ...

s as part of the

inflammatory response Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molecu ...

, which increases the set point for body temperature in the

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...

. The increased set point causes the body

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

to rise (

pyrexia Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...

), but also makes the patient feel cold or chills until the new set point is reached.

Shivering Shivering (also called shuddering) is a bodily function in response to cold and extreme fear in warm-blooded animals. When the core body temperature drops, the shivering reflex is triggered to maintain homeostasis. Skeletal muscles begin to s ...

also occurs along with chills because the patient's body produces heat during muscle contraction in a physiological attempt to increase body temperature to the new set point. When it does not accompany a high fever, it is normally a light chill. Sometimes a chill of medium power and short duration may occur during a scare, especially in scares of fear, commonly interpreted like or confused by

trembling A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving neural oscillations, oscillations or twitching movements of one or more body parts. It is the most common of all involuntary movements and can affect the ...

. Severe chills with violent shivering are called rigors.

Pathophysiology

Chills occur when the

hypothalamic The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamus i ...

temperature set point is suddenly elevated. This could occur due to several causes, including tissue destruction, pyrogenic substances, or dehydration. Due to the body temperature being below the new set point, body mechanisms of raising body temperature, including

vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...

, and shivering ensue. The person experiences this period as extreme cold, even though they might have an elevated body temperature than normal. As the body temperature rises and reaches the new set point, chills stop and the person feels neither hot nor cold. If the factor causing the high temperature is then removed, the hypothalamic set point decreases, but the body temperature is still higher than it. This then triggers the body cooling mechanisms to reduce the body temperature to the new set point, and is experienced as severe sweating, and hot skin due to vasodilation. This phase of the febrile state is known as the "crisis", or the "flush".

Causes

Chills are commonly caused by inflammatory diseases, such as

influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms ...

Malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...

is one of the common reasons for chills and rigors. In malaria, the

parasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...

enter the

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

, grow there and then attack the red blood cells which causes rupture of these cells and release of a toxic substance

hemozoin Haemozoin is a disposal product formed from the digestion of blood by some blood-feeding parasites. These hematophagous organisms such as malaria parasites (''Plasmodium spp.''), ''Rhodnius'' and ''Schistosoma'' digest haemoglobin and release high ...

which causes chills recurring every 3 to 4 days. Sometimes they happen in specific people almost all the time, in a slight power, or it less commonly happens in a generally healthy person.

References

External links

{{General symptoms and signs Symptoms and signs Cold Thermoregulation fr:Frissonnement

Pathophysiology

Causes

See also

References

External links