Does exactly what it says on the packaging: thicken. Derma Activate Thickening Spray is a body-building leave-in spray for fine or thinning hair. It’s infused with Vitamin H, which improves the quality of the keratin inside your hair — stronger keratin means stronger hair that’s less likely to fall out. Provitamin B5 is a powerful moisturizing and thickening agent that’ll strengthen the hair structure over time.