The skin's bacteria join the good fight against ailments

Your skin is a tapestry of ecosystems roughly the size of three bath towels. Complex societies of bacteria, viruses and fungi live in these diverse habitats — from the oil fields of the face and back, to the parched and hairless palms. For decades researchers have argued that some of the skin’s microscopic residents are partly to blame for certain disorders, such as eczema. Now, it seems, bacteria may be part of the treatment, too.

Dr Richard Gallo, a dermatologist and biologist at the University of California, San Diego, USA, and his colleagues recently concocted an innovative microbial treatment for eczema. The recipe was relatively simple. Richard had discovered that Staphylococcus hominis and Staphylococcus epidermidis, typically friendly members of the human skin microbiome, can kill Staphylococcus aureus, which is known to play a role in eczema. So the team swabbed S hominis and S epidermidis from the skin of a few volunteers with eczema, grew the bacteria in the lab, and incorporated the microbes into Cetaphil lotion. Next, they applied the experimental balm to the volunteers’ forearms. Within 24 hours, the probiotic lotion nearly eliminated S aureus from their skin.

The researchers were also able to identify some of the compounds that the beneficial bacteria use to deter S aureus. Richard and his collaborators published their results in Science Translational Medicine. “It’s the first time anything like this has been shown,” said Elizabeth Grice, a research dermatologist and microbiologist at the University of Pennsylvania, USA who was not involved in the experiment. “What remains to be seen is whether this kind of treatment can reduce the severity of skin disease over the long term.”

Modifying the microbes

Only in the last few years have scientists seriously studied how to therapeutically modify the skin’s native colonies of microbes. Understanding this unique microbiome may yield new ideas for treating various dermatologic conditions. Some studies suggest, for example, that people prone to acne carry more of the microbe Propionibacterium acnes on their skin. A disturbance in typical bacterial populations leads to conflict between P acnes and neighbouring species, the theory goes, which in turn triggers an inflammatory response in the skin.

In another study published late last year, Richard and his colleagues injected a beneficial strain of Staphylococcus epidermidis, along with some food that only it could digest, into the ears of mice. The combination treatment encouraged the growth of S epidermidis, which in turn reduced both the number of P acnes and level of inflammation in the mice.

Several private companies are racing to capitalise on a growing consumer appetite for probiotic cosmetics, toiletries and topical treatments. Many microbiologists worry, however, that the science is nowhere near advanced enough to justify the proliferation of these products. While typical antibiotics and antiseptics indiscriminately kill all kinds of bacteria throughout the body, probiotics may be much more selective. And probiotics that successfully colonise the body have the unique ability to evolve in concert with a surrounding ecosystem.