For instance, an animal study conducted in 2018 observed that cinnamon oil improved hair length in male rat subjects . They even compared the effect to about 2% topical minoxidil, a common medicine for hair loss.
Researchers concluded the positive effect could be due to cinnamaldehyde, the active component in cinnamon capable of increasing blood flow to the hair follicles.
Like cinnamon, peppermint can also improve circulation in the scalp, which can promote hair growth.
In an animal study, the investigators divided the rat subjects according to their assigned topical treatment: saline, jojoba oil, minoxidil, and peppermint oil. Of the four groups, the peppermint oil group exhibited “the most prominent hair growth effects.”