This could be intertrigo, which is an irritation of touching skin surfaces in body fold regions such as the armpits, under the breasts, belly, buttocks,or groin. This can be worsened by any conditions causing increased heat, wetness, and friction. At times, this may also be complicated by superficial skin infection with yeast or bacteria. It is important that you cleanse the affected areas daily with mild soap substitutes and keep the areas dry and exposed to the air or use absorbent powders. If overweight, weight loss is also recommended. If it persists, have this evaluated by a dermatologist for prescription medications. Take care and regards.