By Alison Bruzek

New research suggests that your skin may be able to reveal much about your diet and personal habits — including some you were possibly trying to conceal.

Three-dimensional topographic maps created by a group of international researchers show that your skin is a wonderland of bacteria and that slathering on shampoo, lotions, or makeup can leave their traces on you for up to 72 hours after you apply them.

The new maps illustrate the human skin isn’t just made up of human or bacterial cells; it can be changed at the molecular level by what we put on it.

“We actually mapped the chemistry — that has never been done before,” says study author and chemistry Professor Peter Dorrestein.

Much like a cartographer might chart the contours of a land’s hills and valleys, the researchers mapped the many microbes lying on the most exposed organ of the human body — and found a similar amount of diversity.

“If you go to the Sahara you have a unique type of ecosystem and then if you go to the Amazon it’s a very different ecosystem. That’s the equivalent of what we’re mapping here,” says Dorrestein.

One man and woman were swabbed twice over at about 400 skin sites. The bacteria and other microbes discovered were then mapped on a 3-D computer model yielding spotted, Avatar-looking human figures. Each was colored from blue to red, with blue indicating a low abundance of a particular molecule and red meaning a high abundance.

Overall, the researchers found more than 15,000 prevalent chemical fingerprints. Some were what you’d expect — the usual body microbes on the feet, the neck, and the nose. But other discoveries were more surprising, says Dorrestein, like the prevalence of citrus and caffeine on the skin, likely consumed by the subjects.

In addition, they found beauty products, at least, really are skin deep.

The majority of the chemical fingerprints were from beauty and hygiene products — even though the volunteers didn’t shower or use products for three days before swabbing.

However, these residues aren’t necessarily bad for us. Rather, researchers suggest these chemical maps could be used to tell a person’s history — much like human hair can indicate whether someone has taken certain drugs.

In the future, they may even be able to monitor skin disease like psoriasis, or even drug compliance, Dorrestein says. For now, it’s just a matter of mapping and annotating as many people as possible.