Is hot water any better than cold when you're washing your hands?
October 17, 2009
THE CLAIM
Always wash your hands with hot water, not cold.
THE FACTS
With swine flu sweeping across the country, health officials are once again reminding us to wash our hands often to reduce the spread of the disease.
Soap and warm water, in fact, have long been said to prevent the spread of a number of infections, from the common cold to respiratory infections and even the viruses that cause diarrhea. But is warm or hot water really more effective than cold?
In its medical literature, the U.S. Food and Drug Administration states that hot water comfortable enough for washing hands is not hot enough to kill bacteria, but is more effective than cold water because it removes oils from the hand that can harbour bacteria.
But research does not confirm that.
In a 2005 report in the Journal of Occupational and Environmental Medicine, scientists with the Joint Bank Group/Fund Health Services Department examined the science. They pointed out that in studies where subjects had contaminated their hands, and then were instructed to wash and rinse with soap for 25 seconds using water with temperatures ranging from about 5 C to 50 C, the various temperatures had "no effect on transient or resident bacterial reduction.''
In fact, they found no evidence at all that hot water has any added benefit, and noted that it may instead increase the "irritant capacity" of different soaps, causing contact dermatitis.
"Temperature of water used for hand washing should not be guided by antibacterial effects but comfort," they wrote, "which is in the tepid to warm temperature range.
"The usage of tepid water instead of hot water also has economic benefits.''
THE BOTTOM LINE
Hot water for hand washing has not been proved to remove germs better than cold water.
The New York Times