Medieval folks believed bathing could let the devil into you or, at the very least, make you severely ill. They were a little off the mark, but it turns out that traditional bathing is overrated for maintaining health.

Our modern habit of daily scrubbing with soaps and shampoos looks absurd by historical standards—large-scale soap production only started in the mid 19th century and the daily bath didn't really take off until the mid 20th—and some experts think it's harmful.

"Even the most simple of soaps and shampoos destroy the body's natural oils and thus the protection derived therefrom," says Dr. John Fielder, natural hygienist and founder of the Academy of Natural Living in Australia. That protection includes guarding against disease-causing microbes and other nuisances like lice infestation.

Sebum, the skin's natural oil secretion, gives skin and hair its waterproofness, kills germs, sends moisturizing and sun-shielding vitamin E to the surface, and acts as a delivery system for antioxidants and pheromones. You could spend dozens of dollars on soaps to strip it away and several dozen more on cosmetics (most of which are crammed with toxic chemicals to boot) in a tenuous effort to replace its functions.

That's not to say cleanliness is nonessential. According to UNICEF, 30 percent of disease and 75 percent of life years lost in developing countries are due in part to poor sanitation and "risky hygiene behavior," and they recommend regular face and hand washing with soap, ashes, or rubbing.

Nonetheless, what we tend to call "germs" are often good for us. "Far from being our enemies, [bacteria] are our friends, and any activity on their account is a beneficial one," Fielder says.

Maintaining health requires both internal and external cleanliness. People who eat natural diets, live in healthy environments, and perform basic grooming techniques may be less likely to experience illness. If we reduce environmental toxins and eat predominantly raw fruits and vegetables, we have fewer reasons to expect illness.

And you're better off not emulating this guy. Unmitigated buildup of dirt and body waste provides an ideal medium for parasites like scabies. According to Fielder, combatting that is simple and doesn't require soap or even water, as long as you regularly brush the body and hair. "Much of this grooming can occur with the nails as well as the saliva," he says.

Ancient Romans used a similar technique, applying scented oils to the skin and removing dirt and sweat with a metal scraper called a strigil. Fielder's own grooming method, which he has used for at least 40 years, includes exfoliating with sand and rinsing with river water.

"There is a difference between cleanliness and sterility," Fielder explains. "In cleanliness there is bacterial activity, there is life. Without bacteria there would be no life."