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.

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.

Contraception: If there is any likelihood of sexual encounters, pack some condoms. While male condoms are easy to find in most countries, female condoms are very hard to find in third world countries.
Dental equipment: The toothbrush is an archetypal piece of travel equipment. Mouthwash, dental floss and chewing gum can also be useful.
Menstrual equipment: See tips for female travellers
Tissues: Wet tissues, dry tissues, or toilet paper.
Hand sanitizer: In case there’s no sink around.
Camping food for long-term flights/bus trips.
Travel health kit
Eye care equipment

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.

Sanitation on the road
Rest areas 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.

Public baths
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 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 saunas. If you think of visiting them anyway, you can seize the chance to use them also for these needs.

Ceremonial bathing
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.

Hair care
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.

Toilets
Toilets are very different from place to place.

Flush toilet seats are standard in most high-income countries, at least in cities.
Squat toilets are a simpler kind of flush toilet.
Portable toilets are common at festivals and other outdoor events.
Outhouses are common in low-income countries. Even in high-income countries, some countryside settlements and islands have no public water supply, and therefore no flush toilets.
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.

Respect
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 might require swimsuits of a certain shape, or segregation of men and women.