Periwinkle is an excellent all-round astringent that may be used internally or externally. Its main use is in the treatment of excessive menstrual flow, either during the period itself (menorrhagia) or with blood loss between periods (metrorrhagia) It can be used in digestive problems such as colitis or diarrhoea where it will act to reduce the loss of fluid or blood whilst toning the membranes. The New Holistic Herbal by David Hoffmann Pg. 223