The aim of the study was to evaluate metabolite variability in human eccrine sweat using a metabonomics based approach. Eccrine sweat is a dilute electrolyte solution whose primary function is to control body temperature via evaporative cooling. Although the composition of sweat is primarily water, previous studies have shown that a diverse array of organic and inorganic compounds are also present. Human eccrine sweat samples from 30 female and 30 male subjects were analysed using highresolution 1 H nuclear magnetic resonance (NMR) spectroscopy in conjunction with statistical pattern recognition. High-resolution 1 H NMR spectroscopy produced spectra of the sweat samples that readily identified and quantified many different metabolites. The major metabolite classes found to be present were lactate, amino acids and lipids, with lactate being by far the most dominant metabolite found in all samples. Principal Components Analysis, Principal Components-Discriminant Analysis and Partial Least Squares-Discriminant Analysis of the eccrine sweat samples, revealed no significant differences in metabolite composition and concentration between female and male subjects. Also, the variation between subjects did not appear to be correlated with any other clinical information provided by the subjects. Overall, the spectra data set demonstrates the large physiological variability in terms of number of metabolites present and concentrations between subjects i.e. human eccrine sweat samples exhibit a high degree of inter-individual variability.

We demonstrated that localised intradermal administration of SDS induces a limited pain and inflammatory response in humans. Excitation of nociceptors was accompanied by a massive PGE2 release. Employing this experimental model, the relative contribution of endogenous mediators to induce, maintain or facilitate pain and vasodilatation can be investigated.

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