Personal hygiene is important to health and social custom. It's also important for reducing the risk of diseases on the trip, including travellers' diarrhea and infected wounds. While business hotels and other high-end accommodations usually have good bathrooms, outdoor life, budget travel and travel in developing countries can pose a challenge. Clean water is not always available.
See also: Equipment
Airport security is harsh on liquids, but most sanitary products are also sold in air travel size packs. Be prepared to unpack your equipment for the security crew. If you are flying without checked baggage, consider avoiding security hassles by leaving liquids, scissors, and similar equipment at home, and buy it on arrival. Traveling by means other than air will ensure a more liberal luggage policy but if you are crossing borders or taking a public bus, boat or train do check with the appropriate regulations. Carrying of razors, clippers and other sharp objects is also restricted.
If you have toiletries you strongly prefer (like soap for sensitive skin, or bar soap which is not widely available in some European countries) consider taking a supply with you rather than relying on what's provided by your hotel. If you're staying at an AirBnB, hostel, or campground, some or all of the usual bathing supplies (shampoo, conditioner, soap) might not be provided, so check ahead.
Truck stops and campsites might have showers and other sanitation facilities for travellers.
Cleanliness of these places varies a lot, though. Wearing a dedicated set of flip flops into communal showers can help avoid disease like athletes foot.
Visiting a public bath house can be an economical option for a traveller without other access to showers, such as a camper or an urban backpacker. In South Korea and Public baths in Japan you can even sleep there.
Some bath-related venues also offer recreational activities at different price levels: beaches, hot springs, spas, yoga, sport facilities, swimming halls and public sauna. If you think of visiting them anyway, you can seize the chance to use them also for these needs.
Bathing has a role in several religions. Hinduism encourages bathing in the Ganges, at Varanasi and other sites. Christians are initiated by baptism, at occasion done in open water. In Judaism, use of a mikvah is demanded for certain events and circumstances and their remains often indicate a former Jewish presence where no synagogue or other sign of Judaism survives. Islam also knows several ritual washings, but - as can be expected for a religion originating from a desert - sand sometimes stands in for water here.
Hairdressing, including shaving and body hair removal, is usually cheaper in a low-income country. It can also be a good way to get your hair thoroughly washed if you've been traveling off the beaten path without much water or soap for a while, like in a desert.
Main article: Toilets
Toilets are very different from place to place.
In some cultures, the left hand is considered dirty as it is used to wipe your behind when on the toilet. In this case always use your right hand when e.g. eating or shaking hands.
Different cultures have different standards for nudity and expression of sexuality. While a few bath-related venues have a reputation for sexual encounters (such as "gay saunas" in the LGBT community), such activities are taboo at most venues around the world. More conservative countries may require swimsuits of a certain shape, or sex segregation.