A fever can be caused by infection, an impaired nervous system, malignant neoplasms, blood diseases, heatstroke, dehydration, surgical trauma, crushing injuries, and allergic reactions.

The following are several different types of fever.

Rigor is a fever characterized by a sudden shivering attack in which the body temperature rapidly increases.

Hyperthermia occurs when the thermoregulatory mechanism exhausts and fails to compensate for the extra heat produced by the body.

Malignant hyperthermia is a hypermetabolic response associated with uncontrolled heat generation that develops when certain anesthetic medications are administered to susceptible individuals.

Heatstroke occurs due to prolonged exposure to the sun, resulting in the body temperature rising to 104 degrees Fahrenheit or higher. It is characterized by dry skin and central nervous system abnormalities like convulsions, delirium, or coma.

Neurogenic fever occurs when conditions like cerebral trauma, intracranial hemorrhage, or elevated intracranial pressure damage the hypothalamus.

A fever of unknown origin is a fever that persists for more than three weeks and remains undiagnosed even after investigations.