The couple — who share daughters Lincoln, 8, and Delta, 6½ — made headlines recently when they revealed they bathed their kids less frequently as they got older, Bell even saying on The View last week that she's "a big fan of waiting for the stink."
On Monday, the pair further explained their philosophy, making it clear they weren't joking around.
"It's not so much of a joke that I wait for the stink," Bell, 41, said during an interview with Daily Blast Live. "That tells you when they need to bathe."
Shepard, 46, chimed in, adding that they didn't always approach their kids' hygiene that way.
"We had said, we did bathe them religiously for the first few years when the bedtime routine was so vital," he said. "Once that wasn't required to get them to go to sleep, yeah, we took our foot off the gas."
The Armchair Expert podcast host went on to praise his wife. "I'll just say, for America, Kristen has better hygiene than me," he said. "So I think in general, because Kristen wears makeup more often than I do, she has to take it off."
"I'm not in that stuff that often, so I only have to when either a smell is present or I'm in that stuff," Shepard added of his own bathing habits, later admitting that they "could be better."
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Nathan Congleton/NBC/Getty Kristen Bell and Dax Shepard
Bell then pointed out that there is also an environmental reason not to bathe every day.
"This is the other thing — is California has been in a drought for ever," the Good Place star said. "... it's just like, responsibility for your environment. We don't have a ton of water, so when I shower, I'll grab the girls and push them in there with me so we all use the same shower water."
Last month, Gov. Gavin Newsom asked Californians to cut their water usage by 15 percent as the drought worsens. An easy way to reduce water usage is to take shorter showers.
"I don't know, it just happens whenever it happens, I guess," the actress added.
Kristen Bell/instagram Kristen Bell and Dax Shepard
Bell and Shepard's comments come amid an online conversation about routine bathing, sparked on Armchair Expert last month when guests Ashton Kutcher and Mila Kunis said that they only bathe their kids when "you can see the dirt on them."
Bathing babies too much with soap "can dry out his or her skin," according to the Mayo Clinic.
The American Academy of Dermatology Association say on their website that kids ages 6 to 11 "may not need a daily bath," but should at least wash once or twice a week.
"If you can see the dirt on them, clean them. Otherwise, there's no point," Kunis said.