Hye! You are having intergluteal intertrigo
, a candidal infection. Rule out DM, HIV, Anaemia
other disease by blood investigation. Take antifungal tab,anti histaminic tab. Apply anti fungal cream at night and anti fungal powder in day time after bath. Take sitz bath in dettol
mixed warm water. Wear cloths after complete drying the area affected... I hope you will be relieved with this treatment, still if you suffer, consult dermatologist
. Best wishes.