The Hollywood couple, who share six-year-old daughter Wyatt and four-year-old son Dmitri, revealed their parental cleaning approach on Dax Shepard and Monica Padman's Armchair Expert podcast.
Kunis, 37, said: "I didn't have hot water growing up as a child, so I didn't shower much anyway. But when I had children, I also didn't wash them every day. I wasn't that parent that bathed my newborns – ever."
Kutcher, 43, added: "Now, here's the thing – If you can see the dirt on them, clean them. Otherwise, there's no point."
Kunis was born in the Ukrainian Soviet Union and moved to California with her family when she was seven.
Discussing their own skincare routines, Kunis admitted: "I don't wash my body with soap every day. But I wash pits and t*ts and holes and soles."
Kutcher agreed: "I wash my armpits and my crotch daily, and nothing else ever. I got a bar of Lever 2000 that delivers every time. Nothing else."
He added: "I do have a tendency to throw some water on my face after a workout to get all the salts out."
Kunis said she had suffered from terrible acne all her life, and that having children had made her skin much better. But she admitted she also has regular laser treatments.
She said: "I lasered the s**t out of my face. Give me chemicals and laser – if it doesn't burn it's not doing anything."
Kutcher interrupted: "All they're lasering off is all the crazy products you put on your face!"
Kunis and Kutcher met in 1998 when they starred together in Fox comedy That '70s Show. They began dating in 2012 and married in 2015, a year after their eldest child was born.