Discussion: The immune system does not like sharp temperature changes. The sharp fluctuations consume a lot of energy from the body.

The human body can adapt to a hot or cold environment, but not in short time intervals. Sharp changes in body temperatures consume a lot of life energy (not just calories). It is similar to the delay required from an air conditioner before it goes from heating to cooling and vice versa. People with weak immune systems are advised to avoid sharp changes in temperatures.

Link: Immune system boost and rehabilitation.
https://www.sf-healing.com/page/109 (Copy & Paste)