Fever at the first sign of a cold may be caused by a virus acting as an exogenous pyrogen inducing an upward shift of the hypothalamic thermoregulatory point. Colds, also known as upper respiratory tract infections, are characterized by viruses as the causative pathogens. Airborne pathogenic microorganisms invade the mucosa of the upper respiratory tract, causing a local inflammatory reaction and producing endogenous or exogenous pyrogens, which act on the thermoregulatory center’s thermoregulatory point, causing the thermoregulatory point to rise. The thermoregulatory center must re-regulate the body temperature to send out impulses after the rise of the regulatory point, and through increased skeletal muscle contraction to increase heat production, stimulate the skin capillary contraction leading to a decrease in heat dissipation, endocrine changes leading to an increase in metabolism and other ways to raise the body temperature, so a cold will be a fever. Colds not only cause fever, but also symptoms such as chills, muscle aches, fatigue and drowsiness, panic and sweating. Therefore, it is necessary to consult a doctor in time when your body is not feeling well, so that you can have an active diagnosis and treatment.