Researchers have used information collected from hundreds of skin swabs to produce 3D maps of molecular and microbial variations across the body.
"This is the first study of its kind to characterise the surface distribution of skin molecules and pair that data with microbial diversity," said senior author Pieter Dorrestein, professor of pharmacology in the University of California, San Diego Skaggs School of Pharmacy.
"Previous studies were limited to select areas of the skin, rather than the whole body, and examined skin chemistry and microbial populations separately," Dorrestein said.
To sample human skin nearly in its entirety, Dorrestein and team swabbed 400 different body sites of two healthy adult volunteers, one male and one female, who had not bathed, shampooed or moisturised for three days.
They used a technique called mass spectrometry to determine the molecular and chemical composition of the samples.
They also sequenced microbial DNA in the samples to identify the bacterial species present and map their locations across the body. The team then used MATLAB software to construct 3D models that illustrated the data for each sampling spot.
Despite the three-day moratorium on personal hygiene products, the most abundant molecular features in the skin swabs still came from hygiene and beauty products, such as sunscreen.
According to the researchers, this finding suggests that 3D skin maps may be able to detect both current and past behaviours and environmental exposures.
The study also demonstrated that human skin is not just made up of molecules derived from human or bacterial cells.
Rather, the external environment, such as plastics found in clothing, diet, hygiene and beauty products, also contribute to the skin's chemical composition.
"This is a starting point for future investigations into the many factors that help us maintain, or alter, the human skin ecosystem - things like personal hygiene and beauty practices - and how those variations influence our health and susceptibility to disease," Dorrestein said.
The study is published in the Proceedings of the National Academy of Sciences.