Hi,
This could be Intertrigo, which is an irritation of touching skin surfaces in body fold regions (armpits, under the breasts, belly, buttocks, groin, and sometimes between fingers or toes). It can be worsened by any conditions causing increased heat, wetness, and friction. It may also be complicated by superficial skin infection with yeast or bacteria. It is most frequently seen in overweight people, diabetics, people spending a lot of time in bed, diaper users, or anyone with incontinence problems. Redness and breaks in the skin may be observed. The area may also ooze or be sore or itchy.
A bacterial, fungal, or viral infection may develop at the site of broken skin due to the inflammation.The odor may be brought about by this. These self-care guidelines may help: regularly cleanse the affected area gently with mild soap substitutes and keep the areas dry and exposed to the air. If not, absorbent cotton or fabric, as well as absorbent powders, may help. If it persists, have this evaluated further by your dermatologist for proper management. Laboratory tests may be done to determine which organism is present. This link may be helpful: http://en.wikipedia.org/wiki/Intertrigo
Take care and do keep us posted.
Sounds like yeast, although I am surprised it doesn't itch. You can try some over the counter yeast infection cream. Yeast loves the warm moist folds of our skin.
I should have added a little bit more information. There is no itching. Occasionally there is a little bit of a rash and it feels like heat coming from the skin. When the odor is present the skin is sometimes moist.