Calmoseptine. You can find it at Walgreens. Works wonders. The rash will be about gone in a day. It’s soothig, and cooling. Makes you feel better almost as soon as you put it on.
Are you a woman with boob-rash experience?
Mine is a recurring yeast infection. It smells nasty and burns something fierce. I’ve taken to using 100% tea tree oil and that seems to calm it down faster than anything. Stings like the dickens on application, though. I hate it. Have also learned that my insurer does not consider it a factor, even when chronic, in determining the medical necessity of a breast reduction. Fuckers.
I get a rash like this when it gets warm around the male bits…I use straight corn starch and don’t wear undies for a few days …
Well, I hope you now know to skip the corn starch “home remedy” and get the boys some proper medicine next time. Remember, the foot-care aisle, asshole. (-azole, get it?) 
I have a prescription “azole” and also a steroid cream, steroids not to be used more than 2 days in a row. I was told to wash with Cetaphil and dry carefully. And yes, I have Lady Anti-Monkey Butt powder (oddly enough only sold at Ace Hardware around here seemingly). Does a wired bra exacerbate the rash? And what about laundry detergent or fabric softeners? And re: deodorant-powdered ones? And need I wait until the rash is gone? I was told that even when it appears to be gone, I need to medicate the area for another 2 weeks. Glad to know I’m not the only one.
When me and my kid went home from the hospital, they gave us a tin of Sudocreme. It worked wonders to help with and prevent nappy rash. Better then any other product I tried, and I tried other a lot of other because the Sudocrem jar is so… utilitarian.
Anyway, I’ve used it under my boobs for years, applied daily fresh after a shower, and I have no more problems. I also use anah bra that doesn’t chafe anywhere, and is the height of comfort and available for cheap in all sizes. It’s available everywhere in no-brand versions as well, and they are fine and affordable, too.
One more thing that might help, is to let your doctor of doctors assistant look at any moles or flat warts you might have in the under-boob crease. The official term is seborrheic warts.Those can act as gathering points for bacteria and be damaged easily ba chafing. And they are so easily and cheaply removable by touching them with a bit of super cold liquid nitrogen. Ask your doc; it really is n under five minute job and you’ll only think: “I should have done that sooner.”
“ah bras” are not in fact available for all sizes. In particular, if you’re over a C cup. I’ve used something like this bra liner–not exactly, mine are all cotton but this is the shape–and they work well.
Some years ago my doctor said, during my regular exam, “Oh, and if you get a rash under there you can use Monistat to clear it up, it’s available over the counter.” Up to that point I had never gotten a rash under there owing to using deodorant but about three weeks later under the power of suggestion I did:mad:. At the time prescription medication was pretty much free with my health insurance but OTC remedies were not:mad:. So it was like $18 plus embarrassing to buy. But it worked.
The bra liners prevent skin to skin contact if your bra doesn’t. Most of my bras do, but the sports bras don’t, in fact they kinda promote it, and at the worst possible time (when I’m doing something sweaty), and that’s when I use these liners.
My friend is a very well endowed waitress and she swears by this Monistat powder gel to keep all her skin-on-skin areas soothed. Chafing Relief Powder Gel® from Monistat®
I don’t seem to have too much of an issue since I switched to swimming from non-aquatic cardio. But i do have terrible cysts from a skin condition (Hidradenitis Suppurativa) so I’ve got that constant irritation to deal with. In different ways :-/
Something I’ve found helpful, especially if it’s a yeast/moisture problem, is a silver-impregnated fabric (search for that term, or InterDry). I tuck it into creases or folds overnight and it wicks away excess moisture while the silver works on whatever beasties are living there. Spendy, but you can toss it in the washer hundreds of times without affecting its performance.
That is strange. I’m an E cup, but with a relatively small ribcage ( about 80 cm) and I just use an size L. The cup stretches pretty much up to an E of F, but it does become rather monoboob-like, with the cleavage smushed together. This reviewer was not impressed either.Still, worth a try, even if it is just for lounging or sleeping or to give your shoulder bra strap indents a chance to pop back.
There’s also this weird product, a more fancy version of putting a rolled up towel between breasts at night to stop sweating. Surprisingly, it gets good reviews.
With all due respect, I already knew my body was strange. There are many ways to have BOUS, and mine is, rib cage under boob 26.5" and let’s just say this puts me in a G+ cup size. The ad for the ah-bra sucked me in, even though some part of me knew it would not work. I would have got about the same support from a tight-fitting t-shirt.