Our Phones, Ourselves

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Between photos, calendars and other personal information, we generally put our entire lives into our cell phones. Yet UC San Diego researchers have discovered we leave just as much of our lives on our phones as well—at a molecular level.

In a 2015 study, the team noticed that chemical traces stay on our skin for a long time. “And we are transferring them to just about everything we touch,” says study leader Pieter Dorrestein, PhD, a professor in UC San Diego’s School of Medicine and Skaggs School of Pharmacy and Pharmaceutical Sciences. “So we thought—what can left-behind skin chemistry tell us about a person?”

Dorrestein’s team swabbed samples from the cell phones of volunteers, along with each person’s right hand. They used mass spectrometry to detect molecules, which were then compared to known structures in a reference database. Researchers used this information to construct lifestyle “readouts” for each phone’s owner—including diet, preferred hygiene products, health status and locations visited.

For instance, the phones revealed evidence of certain skin creams, hair loss treatments, eye drops and even medications like antidepressants. Food molecules included citrus, caffeine and spices. Sunscreen ingredients and mosquito repellants were detected on phones even months after they had last been used by the phone owners.

“We could tell if a person is likely female, uses high-end cosmetics, drinks coffee, prefers beer over wine, likes spicy food—all kinds of things,” says Amina Bouslimani, PhD, first author on the study and an assistant project scientist in Dorrestein’s lab.

Dorrestein and Bouslimani imagine this information could prove useful in a crime scene situation, where fingerprints or DNA aren’t available or aren’t found in a database. While molecular readouts couldn’t yield a one-to-one match, they could help narrow down the suspect pool.

And the technique could be applied well beyond forensics. Trace molecular read-outs could allow physicians to assess a patient’s medication regimen by monitoring metabolites on the skin. Or clinical trials could become more accurate—medication could be given only to those whose skin reveals they metabolize it well. Skin molecule read-outs may also help monitor environmental hazards, for those in high-risk workplaces or communities.