Rosemary oil.

"You would have to use up 2 kg of rosemary leaves every day to get 2/3 of the effect compared to finasteride. In my opinion, no, for me the lack of clinical trials besides this one puts it back at the bottom of the heap. There isn't much to support it apart from mechanistic reasons which just don't really give it a great chance of working, and the level of this mechanistic evidence is really not that high either. There's also the fact that it's a natural product so the levels of any potential active ingredients in rosemary oil are going to vary a lot depending on where it's grown, when it's grown, how it's harvested, how it's extracted, and how it's stored. Plus essential oils contain allergens and irritants and these could actually make hair loss worse. We can see hints of this in the study: scalp itching and dandruff actually increase for the rosemary oil group. But thanks to other better quality clinical trial evidence we know that any irritation that could lead to hair loss gets outweighed by the hair growth mechanisms for minoxidil. We don't know this for rosemary."