The Dr. Groot Thickening Shampoo was designed to be a strand-plumping, shine-inducing formula for thin, brittle, and aging hair. The formula is said to add a visible increase in hair volume after ...
That's pretty standard for any shampoo made for thin hair, though — these formulas don't tend to contain some of the richer oils that may weigh thinner strands down. Best thickening I'm not sure ...