The information provided here is not a replacement for a doctor. You shouldn't use it for the purpose of self-diagnosing or self-medicating but rather so you can have a more informed discussion with a professional TCM practitioner.
Because it is a herb specifically indicated to treat systremma as can be seen on Flowering Quince's page.
Its main actions are: Relaxes the sinews by increasing the flow of both Blood and Qi. Assists the function of the Stomach and expels Dampness. Facilitate lactation.