This patient has intertrigo, a chronic, recurrent skin condition often seen in obese patients. It is caused by moist conditions in skin fold (intertriginous) areas and is exacerbated by heat and exercise. The rash is confined to the intertriginous area and does not extend beyond these boundaries. Secondary infection with Candida may occur, as in this patient; a clinical clue to this situation is the appearance of multiple small red papules on the periphery of the rash, referred to as “satellitosis.” Treatment consists of keeping the areas dry and well ventilated, with avoidance of occlusive clothing and possibly the use of drying agents (such as powders). Low-potency topical glucocorticoids and antifungal creams may be used to relieve acute flares by reducing the inflammation and treating secondary yeast infection, respectively.

Allergic contact dermatitis in these areas is a diagnostic possibility; however, the multifocal recurrent nature of the rash and its limitation to areas under the breasts and groin make this less likely.

Atopic dermatitis is a red scaly eruption that arises in childhood and presents with periodic flares throughout life. It may occur on flexor surfaces of the arms and legs but does not typically appear under the breasts or in the groin. Atopic dermatitis is extremely pruritic and is frequently associated with allergic rhinitis and asthma.

Cellulitis may often cause an erythematous rash in various parts of the body; however, the findings would be unilateral rather than bilateral or multifocal. It tends to be painful; lack scale, maceration, or other surface changes; and not be accompanied by satellitosis/candidal infection. Also, the recurrent nature of the patient's rash is not typical of cellulitis.