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 damp caverns of the nose, 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 acne and 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, and his colleagues recently concocted an innovative microbial treatment for eczema, a disorder characterized by red, itchy, inflamed skin. The recipe was relatively simple.

Dr. Gallo 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.