Hi, The brown patches most probably would be erythrasma. It is an infection cause by cornybactetium minutissimum. It may be confused with candidal intertrigo. It is a contagious disease. But it dose not cause any symptom except color. I usually advise antibiotic like tetracycline or erythromycine for few weeks. And localy i advise to apply clindamycine gel or fusidic acid cream. You should avoid soap bath as it might excerbate the disease. You may use dettol liquid for bath.. Area should be kept dry. DM,HIV or other immunocompromised vondition should be ruled out. After few weeks treatment,You consult dermatologist.you become alright. I hope you got my answer. Thanks. Dr. Ilyas Patel MD