To the best of my knowledge: While being the modern way, using enzyme powders at low temperatures is not as effective in the context of this thread as raising the temperature using appropriate agents. External washing with soap or similar does not carry/increase a risk of infection while not washing does. As for thrush, cystitis and similar afflictions, the type of clothing worn is also an issue. Some cleaning materials and potion manufacturers and salesmen will however dispute this because they have a vested interest while other "experts" will broadly agree.