Well the suffering of Marie Antoinette during her incarceration has been well documented - Antonia Fraser touches upon it in her biography and Gareth Russell has this to say -
"The Queen’s monthly period had started a few days earlier, but it had quickly degenerated into a frightening case of vaginal hemorrhaging. She had to constantly change her menstrual linens and trying to find the time to do so discreetly, when she was apt to be interrupted by the revolutionary guards at any given moment, was difficult. For a woman who was always so protective over her privacy and mortified by nudity, it was particularly humiliating set of circumstances"
I found this below - sorry for C+P but am tired and paraphrasing is a bit beyond me at the moment -
"Most historians agree that the 17th and 18th centuries were among the worst periods in terms of physical hygiene. Although hot baths and public baths of the Middle Ages still existed, the French regime sounded the death knell for this tradition. The French regime was a period of extreme modesty and, as a result, nudity was frowned upon. It was for this reason that people when washing did not disrobe. Into the 18th century, filth was considered beneficial thus causing people to wash even less. Medical theory of the time was that germs (then called miasmas) floated about in the air and entered the body though the skin, contaminating it. Water (particularly hot water) was harmful since it opened the pores of the skin, making the individual more vulnerable to disease.
It is said that Louis XVI took one bath in his life; on his wedding day. Because of the limited use of water for bathing, soap did not make a major inroad in French culture until the late 1700s. In 1791, Nicholas Leblanc, a French chemist, patented a process for making sodium carbonate from common salt. Sodium carbonate is the alkali that combines with fat to form soap. In the 1700s, cleanliness and hygiene were sought in white linen. Because of this, until the end of the 18th century, most people bathed ‘dry’ or, in other words, using as little water as possible as a cleaning agent. Linen absorbed perspiration, sebum [skin oil], and purified the body, and hence became a sign of the wearer’s sophistication and cleanliness. (This is why Antoinette was so concerned about the lack of linen in the NARRATIVE OF ROSALIE LAMORLIERE).
Therapeutic values were attributed to dirtiness. For example, urine soaked diapers were just dried before using them again; they were not washed. Urine was used as a beauty product to treat acne, among other things. People avoided washing their hair since scalp oil was considered excellent for shiny, healthy hair. As a result, most people had head lice. If you could manage to endure the stench of a person, his house would finish you off. Chances are you would smell several chamber pots. Separate toilet rooms draining to a cesspool weren’t common until the 19th century. Courtiers have written that Versailles had a particular stench; since it was a long distance between chamber pots, one relieved oneself in a corner, any corner.
For the nobility, cleanliness was attempted through the use of cosmetics: perfume and cologne to chase away bad odors, powder to dry greasy hair, etc. Artificial means, predominately wigs, were used to provide the appearance of cleanliness. Fragrances were used in great quantity and containers for them were an important part of early toilet sets. Most scents were heavy and sweet and were kept in glass or crystal bottles with glass stoppers ornamented with silver, gold and other metals.
An increased awareness of the benefits of hygiene in the later 18th century brought a change of attitude toward an unpleasant aspect of life that had been accepted for generations---the prevalence of lice, bedbugs and fleas. Bedbugs were a particularly common nuisance even in royal palaces. Marie Antoinette introduced an innovative remedy when, in the late 1770s, she ordered beds of polished iron from the royal locksmith Courbin. Since the bugs could not nest in the iron bed frames as they could in wooden ones, the royal children were protected from bites. Iron beds then became the standard in hospitals, homes and dormitories.
The peasants, on the other hand, settled for changing the shirt they used as their underclothing a few times a month and washing the parts of their body not covered by clothing (face, neck, hands, arms) quickly with cold water.
Everyone had poor dental hygiene. Since there were no toothbrushes, people settled for rubbing their gums and teeth with a cloth. They would then scrape the remains of food from their teeth with toothpicks.