“People in the past never bathed!”
You hear this one a lot. Is it true? In the sense it’s usually meant (“ewww, people in the past didn’t understand basic hygiene”), no. People have always known that it’s nicer to smell good and not have visible dirt all over you, unless you’re some kind of ascetic making a moral point.
But like so many other things in our lives, smelling nice can be expensive, so the poor can’t necessarily afford to maintain the same standards of cleanliness as the rich. Since basic things like running water were less accessible then than they are now, yes, it is true that many people bathed less than we do today. Past methods of achieving it might also differ from ours, and then of course there are the questions of when and where you’re talking about. Regional conditions and historical periods could change the nature of this topic quite radically.
If you take “bathing” to mean “immersing your body in water,” then it’s a significant undertaking. Where are you getting that water? Bathing in a nearby stream or river is nice if it’s clean — and if there aren’t so many bathers that they’re significantly contaminating the water for people downstream — but it can be very cold. Hauling water by hand to your house is a time-consuming hassle, and even if you have a pump in the kitchen or the yard, you may be ferrying buckets from pump to tub for quite a while. Then how are you going to heat it? Warming up that much water takes a lot of firewood or coal, especially if you want it actually hot as opposed to merely no longer frigid. It’s enough of an investment of resources and labor that in some parts of Europe, the practice was to have members of a household all wash in the same tub, one at a time in order of status — so yes, the patriarch gets a nice hot bath, and then the youngest children are being dipped in filthy, tepid water. Not very appetizing.
Some cultures partly mitigated the hassle by tackling it on a mass scale, with communal baths. Rome is famous for these, though whether the famous system of tepidarium, caldarium, and frigidarium was quite as tidy as it sounds is open to question. The Muslim world inherited this in what is commonly referred to as a “Turkish bath,” which like the Roman baths can be a social nexus along as well as a place to get clean. Japan has also had communal baths for a long time, starting with natural onsen that make use of volcanic hot springs — why heat the water yourself when you can get the planet to do it for you? (Of course, thermal springs often reek of sulfur and other such byproducts.) The challenge here is keeping the place clean, given the number of patrons. A natural spring may circulate the dirty water away for you, but in an artificial pool, things can get nauseating and unhealthy very fast.
You don’t have to immerse yourself in water, though, for it to count as “bathing.” And if you live in a cold climate, it’s probably safer if you don’t. Much easier to haul and heat a small amount of water, then use a rag or a sponge to scrub down, perhaps rinsing with strategic small pours from a jug. You can do your whole body if you have the time and aren’t at risk of hypothermia, but on a day-to-day basis, it’s most effective to focus on key areas: hands, face, armpits, groin, and so forth. (Hair care is complex enough that we’ll leave it to the side for now.) Those “famously dirty” medieval Europeans did this on a regular basis, and the upper classes also rinsed and wiped their hands before eating.
Or you can take an entirely different approach to cleaning yourself. Although the Romans liked their baths of various temperatures, there was a step that came first: being oiled down by a slave, then scraped clean with a strigil, a curved, dull “blade” of metal. This is an eminently sensible move in situations of communal bathing, as it reduces the amount of gunk that’s going into the shared water — and unsurprisingly, Japanese bathing traditions similarly dictate that you scrub down first. The tub is for relaxing in, not for contaminating with soap and dirt.
The Romans also liked to sweat themselves clean, in ways that resemble the Finnish sauna, the Russian banya, and the sweat lodges found particularly among Plains tribes in North America (though those last are used for religious ceremonies, not day-to-day ablutions). By throwing water on heated rocks, you produce steam, and cause your body to sweat. The intended purpose is often more relaxation than cleaning per se, but by rinsing off or entering a body of water afterward, quite a lot can be washed away. The Baltic cultures seem to take a positive delight in what outsiders have sometimes seen as self-torture: first roasting themselves, possibly while thrashing themselves with bundles of wet branches and leaves, then diving into an iced-over pond or rolling in the snow.
Water isn’t the only limitation in regular bathing. Part of the reason for using sweat or oil to clean oneself is that soap can be expensive, especially if you want something that won’t strip half your skin off along with the dirt. Most early soaps were made from some kind of alkali material, often the ashes of various plants, combined with some kind of oil or animal fat. But you can also make natural detergents from other materials, like the seeds of the Chinese honey locust, or the soapberries/soapnuts of the Sapindus genus. In many cases the product is mixed with herbs or some other material to give it a pleasant scent . . . which was distinctly necessary in the case of soaps made with animal fat. Nobody wants to smell like rancid pig all day.
The frequency of bathing has definitely changed over time. The notion that you should take a full-body shower and wash your hair every single day is very modern; it rests on assumptions of indoor plumbing, heated water, inexpensive soap, and the ability to dry both body and hair rapidly afterward. In places where these assumptions aren’t true, we scale our standards back. And as water crises become more and more prevalent around the world, it’s very likely that we’ll see our habits changing in response — returning to a mode where cleanliness still matters, but water is a thing to be used sparingly.