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 genital fungal infection as can be seen on Cnidium Seed's page.
Cnidium Seeds is a Warm herb that tastes Bitter and Pungent. It targets the Spleen and the Kidney.
Its main actions are: Applied topically it clears Damp-Heat on the skin and kills parasites. Tonifies Kidney Yang. Warms and dries Wind-Damp-Cold.
Genital yeast infection Impotence Infertility Vaginal discharge Sore lower back