TMI alert - I will be discussing nether regions using proper names. And this is about not using soap.
When my oldest daughter was 3 and a newly potty trained kid, she started complaining that her vulva hurt. It also smelled bad and was bright red and painful. I asked her pediatrician and she said it was due to irritation from urine due to improper wiping. I extrapolated that to mean I should clean her better. So I did. With all natural soap. And her vulva continued to be stinky, red and painful. I took her to a pediatric gyn who explained that her skin was so thin, the soap was causing the irritation and that irritation manifested as smelliness, red skin and pain. The solution was to discontinue all soaps and chemicals, wash with water only and coat with diaper cream at signs of irritation. I changed the habits and lo and behold, it worked wonders.
Fast forward 7 years. Since puberty, I've had an issue with yeast overgrowth (diagnosed clinically). Even DH developed problems. I finally got it under some semblance of control using boric acid suppositories but still it was an issue. It especially seemed to happen after sex if DH didn't pull out. I mentioned this to a new gyn and she told me point blank that what I was experiencing was a reaction related to irritation from soap. The solution was to stop using soap.
This was a scary idea for me because we are very clean people who like to clean before and after sexy time. I discussed it with DH. We did research and learned this is an issue for men's bits as well, especially the tip of the penis. We gave it a shot under the understanding that any smell issues would be remarked upon and resolved. The results have been remarkable. No more "yeast overgrowth" issues for either and there is no additional smelliness other than a little stronger pheromonal type smells, which are actually nice. Water works just fine.
Soap is now relegated to pits, hands and actual dirt-caked parts.