If confirmed in other studies, spearmint may become an alternative to hormonal treatments for the condition, write the researchers at Suleyman Demirel University's medical school in Isparta, Turkey.
Mehmet Akdogan and colleagues studied 21 hirsute women seen at their endocrinology clinic.
Twelve of the women had polycystic ovary syndrome (PCOS), a hormonal condition that often involves hirsutism. The cause of the hirsutism was unclear in the other nine women.
The researchers asked the women to drink spearmint tea twice a day for five days. The tea was brewed by pouring boiling water over a heaping teaspoon of dried spearmint leaves.
Blood tests showed that the women's levels of androgens -- hormones that include testosterone -- dipped after drinking the spearmint tea for the five days.
It's normal for women to have androgens, but having high androgen levels and hair follicles that are sensitive to androgen can lead to hirsutism, Akdogan's team notes.
The hormonal shift the women experienced after drinking spearmint tea might reduce hirsutism, the researchers say.
However that's not certain, since the study lasted only five days and didn't include any before-and-after measurements of the women's excess hair.
The study appears in the "Early View" online edition of Phytotherapy Research.