According to this study published in the Analytical and Bioanalytical Chemistry journal in 2009, a team of Spanish and British scientists have found a way to trace your travels by testing your hair by using a laser-ablation technique. This technique is able to detect variations in the sulphur isotopes of a single hair strand over time.
During the study, researchers collected hair samples from three volunteers, two of whom were permanent United Kingdom residents while the third had spent the previous 6 months travelling through Croatia, Austria, and Australia.
Results of testing showed that the traveller’s hair strand had considerable variations in the sulfur isotopes while hair strands from the two home-bound U.K. residents had minimal to no changes.
These interesting results could have huge relevance for governmental agencies interested in tracing the lifestyles of international criminals and terror suspects.
I doubt it’s a test that would be applied to ordinary travelers, but if one day, you’re heading through customs and feel a slight tug on your head, it might just be that you’ve suddenly be tagged for a hair test…