Boy, was this summer a scorcher. Even as I write this, hundreds of people in Russia are still dying from heat stroke and the peat-fire pollution. Here in China, with the temperatures raging a couple weeks ago, most newspapers were filled with health advice stories. Discussing how to avoid heat stroke, of course? Uh, not really — many talked about that uniquely Chinese malady, “air conditioning disease“.

Needless to say, air conditioning disease is not a Western, allopathic medicine diagnosis. There is no ICD-10 billing code for this. But here in China, everyone I talk with is completely convinced that many summer colds and illnesses are caused by air conditioning, or at least inappropriate use of it. It’s deeply ingrained with traditional Chinese medicine views of hot and cold winds bearing disease. And my TCM book mentions, “attack by cold and wind in summer will cause headache; fever; no sweating; aversion to cold; pain of limbs; abdominal pain; vomiting and diarrhea.” But is there any actual data out there that air conditioning use causes infections or disease?

I tried a literature search in Pubmed and also talked with fellow doctors and didn’t come up with much. One thing we do know is that some bacteria can thrive in dirty air conditioners, especially Legionnaires disease, which is why proper cleaning is essential. And there is a malady in the west called sick building syndrome, but there is no consensus on that issue at all. Most articles quote one research article, from 1997, that documented an increase in health effects from air conditioners. I did find another 2004 report showing increased work absences with increased exposure to office AC/HVAC systems. However, a 2004 literature review showed that, overall, HVAC systems help more than hurt:

PRACTICAL IMPLICATIONS: The review shows that ventilation has various positive impacts on health and productivity of building occupants. Ventilation reduces the prevalence of airborne infectious diseases and thus the number of sick leave days. In office environment a ventilation rate up to 20-25 L/s per person seem to decrease the prevalence of SBS-symptoms. Air conditioning systems may increase the prevalence of SBS-symptoms relative to natural ventilation if not clean. In residential buildings the air change rate in cold climates should not be below app. 0.5 ach. Ventilation systems may cause pressure differences over the building envelope and bring harmful pollutants indoors.

The Bottom Line?
I didn’t find any articles documenting a compromised immune system from AC use; and the evidence of work-related disease is contradictory. What I did find is massive evidence that heat stroke can kill you, and by far the highest death toll is by elderly folks not having any AC during heat waves. It seems that proper maintenance of your AC and work HVAC systems is important; but overall, when there’s a massive heat wave, an air conditioner is saving a lot more lives than it’s taking.