Metabolomic and lipidomic atlas of human hair across its length.

The stable structure and growth cycle of human hair enables the accumulation of both endogenous and exogenous compounds, making hair an ideal matrix for long-term profiling. However, its exact molecular composition, shaped by root-to-tip variations, remains poorly understood. Here, we present a metabolome and lipidome atlas of human hair originating from a healthy cohort. The Human Hair Atlas maps over 1200 unique molecular species and highlights compounds prone to significant longitudinal variations. Metabolite and lipid levels vary by up to 50% along the length of the hair, underscoring the importance of accounting for segmental differences. We categorized 122 molecules as exposome-related compounds, primarily from personal care products, facilitating biological interpretation. The Human Hair Atlas is publicly accessible ( https://metabolomics.cloud/hair/ ), providing a resource to stimulate research in hair metabolomics, lipidomics, and exposomics, and to explore the potential of hair as a complementary matrix in clinical studies.