Rosemary oil strengthens circulation. As a result, it prevents hair follicles from being starved of blood supply, dying off, and leading to hair loss. Beyond stimulating hair growth, rosemary oil is used to prevent premature graying and dandruff. It may also help dry or itchy scalp.
According to some scientific evidence, rosemary may benefit nerve tissue. Carnosic acid, an active ingredient in the plant, healed tissue and nerve damage in one study. This ability to heal nerve endings may rejuvenate nerves in the scalp too, in turn possibly restoring hair growth.