Hello, You are suffering from blisters on the top of the thigh. It can be due to skin allergy, chaffing, heat rash, jock itch, dermatitis (atopic / contact), etc. Avoid sharing clothes or toiletries. You can take non sedating antihistamine to control and reduce the symptoms of allergy. Wash the affected area with water and antibacterial soap. You can apply hydrocortisone ointment to reduce itching. In case of jock itch or fungal infection apply ointment clotrimazole ointment on the affected area to get relief and reduce spread of infection. Get clinically examined by a GP or a dermatologist to detect any abscesses, boil, carbuncle, etc., underneath the blisters that appears as a lump. Other medical conditions that can cause similar symptoms are cellulitis (infection of the skin and associated tissues), warts, etc. The treatment will depend on the pathology detected. You will be given conservative treatment or suggested surgery in serious medical conditions (lipoma, melanoma, malignant tumors, etc.) if required. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician