Serenoa repens, commonly known as saw palmetto, is the sole species currently classified in the genus Serenoa. The plant is a low shrubby palm that is native of West Indies, and it grows in the coastal lands of North America and other European mediterranean countries. Its fruits contain high concentrations of fatty acids and phytosterols. S. repens extracts have been studied for the symptomatic treatment of benign prostatic hyperplasia. Recently, they have been proposed to treat androgenic alopecia and other hair disorders. We report a new case of hot flashes in a 10-year-old girl using a food supplement containing the extract of S. repens for the treatment of hirsutism. When the girl discontinued the treatment, the hot flashes stopped. A ‘rechallenge' of the supplement was tried and symptoms reappeared. About 4 months after starting therapy, the girl experienced menarche. Exposure to the plant-derived product could be responsible for the appearance of menarche. In our opinion, use of phytotherapeutic agents in pediatric patients should be associated to a better evaluation of benefit/risk profile taking in account the physiological changes that occurs at different ages in this subgroup of population.