Chills is a feeling of coldness occurring during a high

fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...

, but sometimes is also a common

symptom Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

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 produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...

s and

prostaglandin Prostaglandins (PG) are a group of physiology, physiologically active lipid compounds called eicosanoids that have diverse hormone-like effects in animals. Prostaglandins have been found in almost every Tissue (biology), tissue in humans and ot ...

s as part of the

inflammatory response Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

, which increases the set point for body temperature in the

hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

. The increased set point causes the body

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

to rise (

pyrexia Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with body temperature exceeding the normal range caused by an increase in the body's temperature set point in the hypothalamus. There is no single agre ...

), 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 sha ...

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 oscillations or twitching movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, fac ...

. Severe chills with violent shivering are called rigors.

Pathophysiology

Chills occur when the hypothalamic 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 vesse ...

, and shivering ensue. The person experiences this period as extreme cold, even though they might have a body temperature higher 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".

References

External links

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

Pathophysiology

See also

References

External links