Hyperthermia, from the Greek words "hyper", meaning high, and "thermos", meaning temperature, can simply be defined as the elevation of the body temperature. In humans a fever is a physiological thermic resource. Hyperthermia represents a natural immune approach in combating disease since it involves inducing an exaggerated version of the body's own fever state.

Most illnesses are accompanied by a fever. During a fever, the body heats up to eliminate viruses and attack foreign agents. This is direct evidence of the profound healing effects that occur when body temperature rises. Fever acts as a defense mechanism against a number of processes such as infection. One of the most immediate physiological effects of the fever is the acceleration of metabolic processes in general. Fever increases oxygen uptake and renders white blood cells more aggressive against bacteria, fungi or viruses.

False fever created by Far infrared Rays, within physiological limits, can have many beneficial effects and will not produce any harm to normal cells that are able to cope with the higher metabolic demand. Recent studies also show that colds and flu-like illnesses are reduced dramatically if treated in the early stages with FIR heat therapy. The Aesta Sauna Dome and Aesta Ion Mat raise the core body temperature and give the user the gift of enhancing one's own immune systems processes.