The present disclosure relates generally to methods and apparatus for determining components and associated conditions in a dermatological sample, and preparing personalized cosmetics or treatments. In particular, the present disclosure relates to the use of surface desorption ionization-mass spectrometry methods and apparatus to assay dermatological samples. The method and apparatus can allow real time analysis of sample molecules, such as in skin and hair, for molecular diagnostics in dermatology, dermatopathology and the preparation of personalized cosmetics.