Hello, You have dark skin on your buttocks and there are many dark spots also. The skin in the folds on the buttocks have a higher concentration of melanocyte so the color appears darker. The buttocks also experience more friction, which could lead to skin irritation and eventual hyperpigmentation. Acne also leave dark spots. You are suggested to keep the area clean, avoid direct exposure to the sun. Exfoliate the affected part at least once a week. Change clothes if you have sweated., wash in in hot water. Wear loose soft fabric that reduces friction. Continue to use hydroquinone, it works by temporarily deactivating the number of melanocytes in the skin. The more pigmented the skin, the longer it’ll take to clear. 6 months -2 years. You can apply topical creams and ointments like retinoids, azelaic acid, and chemical peels. Use one at a time, else it can cause more dark spots if reaction occurs. You are suggested to get clinically examined by a dermatologist. You may be suggested treatment with laser therapy. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician