Hygiene

After a while, Sims start to get dirty, and if they get very dirty, they start sniffing themselves and saying, "Ewww!". Bad hygiene will seriously affect Sims' mood and social skills—bad hygiene won't get a Sim promoted at work either. Therefore, it is necessary to take a bath or shower when the hygiene meter slips into the red—a hot tub also works, but not as well, although it can boost the social and fun bars. Washing one's hands after going to the bathroom also improves this rating, as does brushing teeth or gussying up in the mirror. In order to facilitate the latter activities, be sure to have a medicine cabinet, bathroom cabinet or mirror and sink. Sometimes, the shower leaks after a Sim has been in it, so it's handy to have a mop ready.

Activities that decrease hygiene
Some activities or events cause a Sim's hygiene need to decrease faster then normal. Some examples are:
 * Most forms of exercise unless a Sim uses the "Don't Break a Sweat" tone or has the Gym Rat reward trait.
 * If a Sim's bladder need bottoms out, they will pee themselves which will instantly bottom out the hygiene meter.
 * Being near a fire.

Hygiene on community lots
Most community lots will not have any ways of increasing hygiene other than sinks. In The Sims: Superstar, some Studio Town lots have steam baths and hot tubs, but none of them boost hygiene sufficiently. Therefore, it's best to get the hygiene meter as full as possible before going out.

In The Sims 2, Sims with less than 2 Neatness points will take a sponge bath on community lots if their hygiene meter drops to the point where they begin to stink. This action is completely autonomous and cannot be prompted, nor will the action come up again during a visit if the player interrupts it. If left in the queue, Sims will proceed to the nearest sink and bathe themselves, raising their hygiene bar to approximately 75%.

Bathing isn't a problem on Vacation Island, as most lots at least have showers, and resort lots have baths. Likewise, it's not a problem in the Bon Voyage vacation destinations, because there are baths and showers in the hotels.

In The Sims 3, Sims with the inappropriate trait have the option to take a sponge bath at any sink. Differing from The Sims 2, this action can be prompted by the player.

Hygiene and other life states
Servos, PlantSims, SimBots and Plumbots have no hygiene motive, though a PlantSim's water motive has some elements of hygiene. Bigfoot is largely indifferent to his own hygiene, and will not bathe unless directed to by the player.

Other ways of affecting hygiene
In The Sims, The Sims 2, The Sims 3, and The Sims 4, there are alternative ways of raising, or maintaining, hygiene.

In The Sims: Makin' Magic, magical children can use the No More Puddles? charm to take a magical "bubble bath". For adults, the Magic Mood charm can boost all motives, including hygiene.

In The Sims: Livin' Large, the blue potion that can be made with the chemistry set maxes out three random motives, though there is no way to be certain that Hygiene will be one of them. In The Sims 2, Sims can use The Eclectic and Enigmatic Energizer to raise all motives, including hygiene. In The Sims 3: Ambitions, Sim inventors can also invent the Floor Hygienator, which is placed on the floor and improves hygiene levels slightly when walked over.

In The Sims 2: Open for Business, a successfully crafted Snapdragon Bouquet will periodically boost the hygiene of Sims and pets in the room. In The Sims 2: Seasons, the career rewards for the Adventurer and Journalism careers will do this.

In The Sims 2: Apartment Life, the good spell Benemoodus Simaethe increases all of the motives including hygiene, while the neutral spell Cleanus Corpus only boosts hygiene.

In The Sims 3, a Sim can buy the Dirt Defiant lifetime reward (for 15,000 Lifetime Happiness points), which will make it take longer before the Sim with that reward has to take another bath.

In The Sims 3: Supernatural, witches can cast Hygiene Charm and Hygiene Curse to increase or decrease hygiene.

In The Sims 3: Into the Future, using Power Cleanse option with a Sonic Shower gives the Sim Pristine Protection moodlet, which stops hygiene decay for 5 hours.

In The Sims 4, a Sim can buy a special potion from the aspiration reward store for 100 satisfaction points, which will immediately fill the hygiene need. The Antiseptic trait can also be bought for 3000 satisfaction points, which makes the Sims hygiene meter decay slower.

Pets
Pets, like Sims, have hygiene motives and need to be fulfilled. Cats will clean themselves, but dogs will need to be washed by a Sim, which can sometimes be hard if a dog likes to be dirty. In Unleashed there are dog baths for dogs, but in Pets dogs will need to be washed in regular bathtubs. When the dog jumps out of the bathtub, they will leave a puddle behind. So it's handy to have a mop ready for that too.

Higiene