Hair hydration is one of the effects that consumers most expect when using a cosmetic hair product. The purpose of this study was to combine differential scanning calorimetry (DSC) and gas chromatography (GC) techniques for a precise evaluation of the water content in hair fiber. DSC allowed determination of the bonding strength of water to hair fibers by quantifying the amount of energy required to remove the water. The amount of water thus removed was determined by GC. Post-treatment sensory evaluations of hair tresses were conducted to determine whether the values obtained with these techniques correspond to the moisturizing sensation perceived by consumers.