While watching a show or reading a book set in the 18th century, you best count yourself lucky that they are not realistic in terms of hygiene and that Smellovision is not a thing. It may look like it is all proper manners, powdered wigs and puffy dresses but under that there was some very filthy people.
Most historians agree that the 18th century was the worst in terms of hygiene. Especially during the latter half when the Industrial Revolution started to ramp up and the city air filled with soot and smog. The cities were crowded to the brim and hygiene practices were far and few between.
Bathing in the 18th century was more of an activity for fun rather than hygiene. In fact, many in the 18th century believed bathing to be harmful so thus even in rich households it was done in moderation. The theory back then was that germs, then known as miasmas, were everywhere and that they could enter the body through the skin. Bathing the skin, especially in hot water, left the pores open so that these miasmas could seep in. So in lieu of dipping themselves in water, most nobles would take "dry" baths instead. This involved wiping away perspiration and skin oil with clean linen. This did not open pores and was thought to keep one from smelling too badly. Too bad that, as we all know now, body odor is not caused by sweat but the bacteria on the skin that grows and begins to stink.
Seeing that people avoided bathing, they also avoided washing their hair. They enjoyed dirty hair as the scalp oil was considered great for providing soft, silky hair. As a result of this, many people--rich and poor--were riddled with head lice. Of course, a popular remedy for this was to rub mercury on their scalp. This of course lead to madness and death, but at least the maddening lice died.
It's hard to believe, but the poor were actually more likely to be bathed than the rich. Though they did not soak in baths but a remedy for bedbugs (which were rampant) was to quickly wash the face, arms, and legs with cold water to get the bugs off your skin after sleeping.
It is no secret that before modern plumbing or even outhouses people used small pots known as chamber pots to do their business in. These pots, however, would have to sit for awhile before a servant (if you are wealthy) or yourself (if you weren't) could empty it. Leaving your household with a smell that just could not be purged.
Back then the smell of urine and feces was nothing to be ashamed of. The smell was everywhere. If you weren't smelling the sweet smell of some heavily perfumed noble, guess what wafted through the air? People would empty their chamber pots into the streets through their windows and if they were polite, they might even warn anyone below them. So urine and feces would be prevalent in the streets.
Interestingly enough, the tradition of the gentleman walking on outside of a sidewalk by the street originated from this. It was to prevent the lady from being splashed from passing carriages, often the water splashing them would be a mixture of water, urine and feces.
Though often times urine from chamber pots was kept. It was thought to be medicinal to acne and was used as a beauty product.
A Ladies Time of the Month
Many people wonder how women treated their time of the month before the invention of pads. Though ancient Egypt is coined with creating the first tampon from softened papyrus, they were not used in the 18th century. Like they believed dirt was healthy, women believed that stopping the flow of blood to be hazardous and to cause more intense bleeding. Some women just let gravity do its work while others wrapped their nether parts in cloth to catch the flow.
Teeth cleaning was actually relatively modern in the 18th century. They did not have toothbrushes, but they used tooth picks to clean food from their teeth and a piece of cloth to rub over the teeth and gums to clean them.
Tooth paste did make its emergence in the early 1700's by an Italian company called Marvis (that still makes tooth paste today). However it was a luxury good and many poor folk felt they could better spend their money buying meat for slew rather than fancy Italian tooth polish.
While people were quite filthy by today's standards, they at least did not enjoy it. Dirt was seen as more of a way to prevent disease, not because they loved being smelly and dirty. So thus, nobles in many countries adopted ways to look clean while not actually being so. With them, they bore the unique fashion of the 18th century. Nobles powdered their hair to give it a clean look or just wore powdered wigs to cover their hair. Particularly complex and puffy wigs also contained their head lice and, on occasion, maggots. So next time you see a dashing young rogue walking down the way in your 18th century drama, think about how he would actually look with powder in his hair or a wig with odd things crawling in it.
In the 18th century noble men and women went to great lengths to make themselves appear clean that they looked almost unnatural. They used whitened lead power not only on their wigs, but on their faces as well to make them look as white as possible. Up until the 1920's pale skin was a sign of wealth, so they whitened themselves as much as possible to differentiate themselves from the lowly day laborers. Since their face powder contained lead, if often lead to permanent blemishes on their faces. To cover these they applied melted beeswax to the face and powdered over it. So in that day, if you got too close to the fire you might see a few faces melt.
If they had some form of deformity, such as a smallpox scar on the face, the nobles of the 18th century would add circles of black silk to their faces to cover them.