Sebum levels are widely used to evaluate skin and scalp greasiness and to test the cleansing efficacy of skin cleansing products. Techniques commonly involve sebum sampling using Sebutape™ or solvent-based swabs. TRI uses FTIR spectroscopy to measure the sebum levels in vivo without the need for any sebum extraction processes. The flexibility provided by the optical probe attached to the IR spectrometer makes it easy to investigate all parts of the body, including the scalp. Moreover, multiple parameters such as sebum level and composition, skin hydration, and product retention can be simultaneously evaluated with a single measurement during a clinical test. FTIR imaging can also be used to visualize the sebum distribution on the skin surface in pre-clinical tests at TRI. Images can provide a strong visual representation of skin cleansing.