I simply part my hair with a comb, apply the serum from front to back along each section, and then massage it in. How to Use the K18 FutureIQ Hair Longevity SerumIt’s best to use this formula as a crucial part of your evening wind-down routine. The serum can be applied post-wash to damp or completely dry hair (I prefer the latter). That said, it’s important to consider this serum as part of an overall wellness regimen, rather than the sole solution to hair concerns. “Thinning hair could be androgenetic alopecia, telogen effluvium, traction, or scarring alopecia,” Divya Shokeen, MD, a board-certified dermatologist, previously explained.