People should go with the rules of nature. Summer is the time to sweat," says Xu. "It's a natural process for the body to respond to the outside environment, and adjust itself through the constricting of blood vessels, and nerves. In this sense, air conditioning is a reactive restrain of the body against nature."

As the body tries to continually adjust between the outside and the cool air-conditioned indoor environment, Xu says the temperature compromises people's immune systems, and gives diseases a chance to flourish.

Xu's hospital has witnessed increasing cases of colds, fever and pneumonia during the summer, many of which are related to the use of cold air conditioning, according to the doctor.

"Air conditioning might induce infection of the upper respiratory tract, cause colds, throat pain, pharyngitis, and even pneumonia," says the doctor. "Besides, temperature differences can aggravate rheumatism among old people, and trigger some problems among children."

Xu says people's health is a dynamic balance between their immune system and pathogenic factors.