Army life in the 1860s differed significantly from the modern military. Although living and sleeping arrangements were as close or closer than they are today, the fact that the majority of soldiers lived outside throughout the war, with the latitude to wash and attend to sanitary matters out of sight of comrades, made it possible for females in the ranks to avoid the scrutiny that would give them away. Also, societal standards of modesty ensured that no one would question a shy soldier’s reluctance to bathe in a river with his messmates or to relieve himself in the open company sinks.
Stg. Herman Weiss, 6th New York Heavy Artillery, explained to his wife how a woman in his regiment had maintained her male persona for close to three years: “It is no wonder at all that her tent mates did not know that she was a woman for you must know that we never undress to go to bed. On the contrary we dress up, we go to bed with boots, overcoat and all on and she could find chances enogh when she would be in the tent alone to change her clothes.”
Daily bathing, particularly for soldiers on the march, was not a concern as they often went for months at a time without bathing or changing clothes. Women who sought privacy would not have aroused a great deal of suspicion, especially since they had already established reputations as modest men when they chose to use private toilet areas.
But what about menstruation? Little is known about how 19th century women dealt with their monthly cycles, but it’s presumed women soldiers used folded rags to protect their clothing and mask the odor of blood. Washing or disposing of this evidence may have been a problem for them, though bloody rags could have been explained away as the used bindings of a minor injury.
Menstruation might have ceased to be a problem, particularly during a campaign season. It’s possible that many female soldiers became amenorrheic while in the army. Amenorrhea, or the cessation of menstruation, is caused by intense athletic training, substantive weight loss, caloric deprivation or poor nutrition, and severe psychological stress.
 Until disposable sanitary pads were created, women often used a variety of home-made pads which they crafted from various fabrics, leftover scraps, grass or other absorbent materials to collect menstrual blood. Many probably used nothing at all. The first commercially available American disposable napkins were Lister's Towels created by Johnson & Johnson in 1896, though for several years they were too expensive for many women to afford. When they could be afforded, women were allowed to place money in a box so that they would not have to speak to the clerk and take a box of Kotex pads from the counter themselves. It took several years for disposable menstrual pads to become commonplace. However, they are now used nearly exclusively in most of the industrialized world.