Hello, Your sister should take care of your hygiene. She should take bath regularly and wash the area affected gently with a mild soap. Applying antibacterial cream or ointment like Soframycin will be helpful. If it is itchy, she can apply ointment hydrocortisone on the affected area, it will help to reduce itching & discomfort. She should not touch, scratch or pick as it will only lead to spread. If needed she can cover the blister with a bandage or gauze. Do not let it get infected. Taking antihistamine at bedtime will help to reduce the symptoms of allergy and inflammation. It will help to control symptoms. She should avoid sharing clothes, towel, bedding or toiletries. She is advised to stay away from dust, pollen, paint, fumes pollution, poison ivy and food that triggers the symptoms. She can take a course of antibiotic like doxycycline if the symptom is persistent. She is advised to get clinically examined by a Dermatologist. Get few required tests done to detect scabies, contact dermatitis, allergic dermatitis, any underlying medical condition that is causing a flare up, STD tests to be on the safer side. Her treatment will depend on the pathology detected and severity of symptoms. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician