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Which signs commonly appear during acute inflammation?
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Acute inflammation is characterized by four cardinal signs, originally described by the Roman writer Aulus Cornelius Celsus:
- Redness (rubor): Caused by the dilation of small blood vessels (vasodilation) in the injured area, which increases blood flow.12
- Heat (calor): Results from the increased blood flow to the site.1
- Swelling (tumor): Also known as edema, this occurs when increased blood vessel permeability allows protein-rich fluid, cells, and other substances to accumulate in the tissues.132
- Pain (dolor): Induced by the distortion of tissues from swelling and by chemical mediators such as serotonin, prostaglandins, and bradykinin.1
A fifth sign, noted by pathologist Rudolf Virchow, is the loss of function in the affected area, which may result from pain inhibiting mobility or severe swelling preventing movement. These responses facilitate the arrival of white blood cells, particularly neutrophils, which act as phagocytes to clear debris and combat potential infection.124