PUBLIC HEALTH
September 28, 2015

Antibacterial Soap Flunks Another Test

Antibacterial soaps release dangerous chemicals into the environment as well as our bodies. But do they at least kill germs?

You may want to take a long last look at your antibacterial soap, if you are still using it. There are already good reasons not to buy antibacterial soap. And now researchers have found another one: in laboratory tests, it leaves hands no cleaner than regular soap does.

As far back as 2010, the Food and Drug Administration (FDA) said that there was no evidence that antibacterial soaps provided any more benefit that plain soap. In 2013, the FDA proposed that manufacturers of antibacterial soap either provide proof that the soaps were more effective than plain soap and were also safe for long-term daily use, or they would have to re-label these products or reformulate them.

In nine hours, the antibacterial soap killed significantly more bacteria. But who washes their hands for nine hours?

The current study provides no such proof. Quite the contrary.

The researchers looked at the effectiveness of antibacterial soap that contains triclosan, one of the two active ingredients commonly used in antibacterial soaps and body washes. Triclosan tends to be found in liquid soap, while the other antibacterial additive, triclocarban, is most often found in bar soap.

They first compared the effect of triclosan on 20 different types of bacteria inside of test tubes. These bacteria were exposed to plain soap and to soap containing 0.3% triclosan, the maximum amount allowed in antibacterial soap. Exposure was for various times at both room and warm water temperatures (71ºF and 104ºF; or 22ºC and 40ºC).

In nine hours, the antibacterial soap killed significantly more bacteria. But who washes their hands for nine hours? In the 10, 20 and 30 seconds more typically used by people to wash their hands, there was no significant difference between the amount of bacteria killed by triclosan-containing soap and plain soap.

The scientists also tested effectiveness during actual hand washing by 16 healthy volunteers. First, the bacterium Serratia marcescens was applied to the volunteers' hands, and then they washed their hands for 30 seconds in warm water with either regular soap or soap containing 0.3% triclosan.

Once again, antibacterial soap was no more effective than plain soap at eliminating bacteria.

Chemically, triclosan is a chlorinated organic compound. When flushed down the drain, it becomes chlorinated waste that is harmful to many types of aquatic life. While not proven to be harmful to people, there is some evidence that it might be. Among the concerns raised by studies are that triclosan:

  • Accumulates in breast milk and the food chain;
  • May act as an endocrine disruptor;
  • Weakens muscles in fish, mice and isolated heart muscle tissue in the laboratory.
  • Why use a product that may be harmful and has no known benefit, especially when there is still plenty of conventional soap on the market?

    The study appears in Journal of Antimicrobial Chemotherapy.

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