How long will it take for a vellus hair to change back to terminal hair once transformed?

Vellus hair, which is fine and soft, can be transformed into terminal hair (thicker, coarser hair) through processes such as hormonal changes, but once vellus hair has been transformed into terminal hair, it does not revert back to its original vellus form. This transformation is often irreversible due to the changes in the hair follicle and the biological makeup of terminal hair, which is deeply rooted and supported by a more robust blood supply compared to vellus hair. Hence, the understanding that once hair has transitioned to a different type, the original form cannot be restored is critical in hair biology and the context of electrolysis and laser treatments. This knowledge is particularly important for practitioners involved in hair removal and understanding hair growth patterns.