European peony (Paeonia officinalis) has a long history of use in traditional medicine systems, particularly in European herbalism and also in Traditional Chinese Medicine (TCM, where Paeonia lactiflora, a closely related species, is more commonly used). Traditionally, peony root was utilized to address a range of women's health issues, including menstrual irregularities, dysmenorrhea (painful periods), and other gynecological concerns. Herbalists believed peony could help "regulate the blood," relieve spasms, and balance hormones affecting the menstrual cycle.

While the traditional use is well-documented, especially in historical herbals from Europe and in TCM texts, scientific validation for the efficacy of European peony (Paeonia officinalis) specifically in treating menstrual irregularities is limited. Most modern research focuses on Paeonia lactiflora (white peony), which contains compounds such as paeoniflorin that may have hormone-modulating and antispasmodic effects. Some clinical studies—primarily in East Asia—suggest that peony, often in combination with other herbs like licorice, may help restore menstrual regularity, particularly in conditions like polycystic ovary syndrome (PCOS). However, these findings cannot be directly extrapolated to European peony due to differences in species and phytochemistry.

In summary, the use of European peony for menstrual irregularity is primarily supported by traditional usage, with a modest level of historical evidence but a lack of robust scientific studies specific to this species.