Unlock the secret to fuller, thicker hair with the Nioxin Pro Clinical Density Defend Hair Booster Serum. This advanced 100ml leave-on treatment nourishes and strengthens hair from root to tip. It creates a protective barrier around hair cuticles to shield against damage while enhancing the diameter of each strand, resulting in a visibly thicker appearance. Formulated for progressive thinning, it targets receding hairlines and thinning crowns. Apply to the roots and leave it in without rinsing. Scientifically tested, this serum delivers noticeable results, transforming thinning hair.