I’m glad I’m not the only one who thought of our friend, Doctor Science.
I love it!
The idea is that underwear and showering are both on a 24-hour cycle but 12 hours apart. This way the body and clothes can transfer the healthy bacteria back and forth sooner.
And how exactly does that not give a chance for the unhealthy bacteria to transfer?
Hmmm… I just had garlic and mushroom pizza for lunch. For dinner I’m having Bush’s beans simmered with lots of fried white onion and barbecue sauce, mashed potatoes made with garlic butter, and leftover roast beef that had been roasted with a garlic steak rub. Maybe later some onion rings for a snack. 
I should get me one of those canine scientists to diagnose my subsequent condition scientifically!
Although I seriously think the onion and garlic avoidance theory is BS. To the extent that different people – and even the same people at different ages – are susceptible to different levels of BO, it probably has to do with differing amounts of surface bacteria, which may be related to things like lifestyles, susceptibility to perspiration, and differing protein availability or pH levels in the subject areas, among other things.
Disclaimer: Although I am a dog with a sensitive schnoz, I don’t have a Ph.D. in this subject! Just natural canine talents.
And to add: fungus stinks. If you have fungus issues get the right stuff for cleaning it, get a doctor to give you meds.
I’ve heard of healthy bacteria inside the body (i.e. gut flora), but what healthy purpose do bacteria serve outside of the body?
Long ago I worked for somebody like that. This was an office job, not out in the field. He always looked good, his clothes were freshly pressed, and he always had an eye-watering nose-curling stench of sulfur and ammonia. Take the worst BO you’ve ever smelled and turn it up to eleventy. I’ve never experienced anything like it before or since.
Then one day he came to work and didn’t stink at all. I was there about another 6 months but for the rest of my time with him he smelled no differently than any other office worker.
I don’t know what he changed, but the result was dramatic.
I’m not touching this with a Ten-Foot Pole. Nor will I link the appropriate ZZ Top song.
I’m Bad, I’m Nationwide?
Here’s another vote the OP’s idea is senseless.
If showering harms “good” & “bad” bacteria equally and re-inoculating your skin w dirty underwear transfers “good” and “bad” bacteria back to the skin equally, you’re not really accomplishing anything.
For this scheme to confer benefit you’d have to assume that showering harms “good” bacteria more than it does “bad”, or that re-innoculating transfers more “good” than “bad” bacteria back to the skin. There’s no reason to believe a priori that either of those things is true.
Now it is true that some people stink lots. Other people don’t stink much. Some people shower often, and some people shower only rarely.
I’m going to go waay out on a limb here and suggest that personal body chemistry and your personal skin flora have a lot to do with how you smell. The folks who quit showering then discover they stench pretty quickly abort the experiment. (That’d be me). The folks who quit showering and don’t stench are the ones who keep doing it. And they probably don’t stench when they do shower either.
Bottom line: non-showering non-stinky people are evidence of a self-selecting correlation, not a causation.
I shower at least once a day. I literally cannot imagine skipping a day. I used to work with someone who was very sensitive to the odor of garlic. I love garlic. I sometimes roast an entire head and we eat it spread onto bread.
Anytime I ate garlic that way she could tell the next day. She could smell me when I walked in the door.
Same as (for the most part) the inside. Fill up a niche otherwise available to bad bacteria.
When I was on chemo I had the best skin of my entire life, and no BO … pretty much all my microbiome was killed off. No blackheads, whiteheads, deep annoying cystic acne, no pit or crotch BO … it was amazing [not that I want to go on 5FU again - chemo is more or less living hell]
I still only wash my hair once a week, but it gets combed every day [sometimes more than once a day, I use a boxwood comb to spread the oils out] and I shower twice a week [sometimes only once a week - I skipped everything last week because the power went out and the deep pump was not refilling the tank and there was a propane feed issue I didn’t want to screw with, and mrAru wasn’t around to fix it. So, until he gets here today, average temp outside, hovering around 32F, inside, hovering around 40F. Dress warm and snuggle the cat a lot =) ]
When I was on chemo I had the best skin of my entire life, and no BO
Same! And no right armpit sweat odor for years after radiation.
Gotta ask… how do you live in South Texas and avoid eating onions and garlic?
Upon reflection, I believe he meant raw onions and garlic. For example, raw onions on a hamburger or chopped raw onion on top of your enchilada. I dunno. Can’t ask, as he died earlier this year.
The weird thing I recently read about hygiene is over 1/3rd of Brits surveyed admitted to only changing their sheets once a year. Since then I’ve wondered what day they pick. January first to ring in the new year? Christmas? Their anniversary?
Sounds like something that college students would do, taking sheets home over Christmas break to get washed.