Numbers cited for hair loss only take into account the absolute number of hairs. They do not reflect the fact that the regrowing hairs are lighter and thinner than before, which also adds to apparent clinical hair loss. Hair color was measured by calculating the absorption coefficient from the hairs’ transmission of 700 nm light. Hair diameter was measured from digital photographs. The study showed that the regrowing hairs appeared lighter (with a transmission coefficient times higher than the value before treatment) and were thinner (with a decrease in the mean hair diameter by ) than the original hairs
