Dix set guidelines for nurse candidates. Volunteers were to be aged 35 to 50 and plain-looking. They were required to wear unhooped black or brown dresses, with no jewelry or cosmetics. Dix wanted to avoid sending vulnerable, attractive young women into the hospitals, where she feared they would be exploited by the men (doctors as well as patients). Dix often fired volunteer nurses she hadn't personally trained or hired (earning the ire of supporting groups like the United States Sanitary Commission).