More than one million North Americans are diagnosed each year with skin cancers. Twenty percent of people have the bacterium called Staphylococcus epidermidis living on their skin. It produces molecules that have been shown to slow or stop the development of skin cancers in mice (Science Advances, Feb 28, 2018:4(2):eaao4502).
Skin cancers can be caused by excessive exposure to ultraviolet rays from the sun. The bacterium Staph epidermidis makes a chemical called 6-N-hydroxyaminopurine (6-HAP) that can block DNA synthesis of cells. It can block the growth of rapidly-dividing cells that are cancers, while it does not appear to block normal cells because normal cells make an enzyme that inactivates 6-HAP.
In this study, the researchers injected 6-HAP into mice with skin cancers every 48 hours for two weeks and found no evidence that it was harming the mice. Then one group of the mice had their skin colonized with bacteria that did not produce 6-HAP and their cancers continued to spread. Another group had their skin colonized with Staphylococcus epidermis bacteria that produce 6-HAP, and the growth of cancer cells slowed down dramatically. The researchers found that injecting 6-HAP directly into the bloodstream inhibited the growth of melanoma cancer cells by more than 50 percent. They also showed that applying Staph epidermidis to the skin of mice helped to prevent group A strep, a bacterium that causes infections from strep throat to cellulitis and rheumatic fever and kidney damage.
These researchers concluded that Staph epidermidis may help to prevent skin cancers (melanoma and squamous cell carcinoma) and ultraviolet-induced pre-cancers in humans. This is very preliminary data that may or may not be supported by future studies. We do know that there are many types of beneficial bacteria that live on human skin and help to keep harmful skin bacteria from growing there. In the future, we may learn how to apply healthful bacteria to the skin.
This study does send a message that perhaps a person can wash too often and lose the protection of beneficial bacteria. As of today, there is no evidence that washing your hands often is harmful because the thicker skin there appears to help protect you from infections. On the rest of your body, I suggest using water or gentle soaps such as Ivory and perhaps avoiding anti-bacterial soaps except where they may be desired for odor control. See my previous report on anti-bacterial products