What does hair mousse do for hair? Hair mousse is typically a foam that you can apply to your hair style to give your hair hold, definition and to protect your hair from unwanted curls and flyaways. Mousse can help with frizzy hair and to define wavy and curly hair. Kerastase hair mousse products suit a variety of needs. Our best-selling Densifique Densimorphose hair mousse featuring Hyaluronic Acid helps to thicken thinning hair and give hair a more dense and voluminous appearance. Our preferred hair styling mousse, Mousse Bouffante is a classic volumizing and bodifying hair mousse for all hair types. Find the best hair mousse for your hair styling needs