Hello, If your grand mum has tested negative to allergy test, then she has either a sensitivity to a less common allergen or the rashes are due to underlying medical conditions. Medical conditions like diabetes, contact dermatitis, insect bite, xerosis, scabies, poor hygiene can be a cause of her symptoms. Get a complete medical check-up to detect any underlying disease. She has to keep her blood sugar level under control at all cost. She may need a nurse / attendant to take care of her and help her maintain hygiene. She needs to take bath regularly and all her clothes should be washed in hot water and Dettol / Savlon and dried in the sun. She should wear clean loose fitting cotton clothes. She should not keep her skin dry, after bathing she is advised to apply Lacto-calamine lotion or a herbal moisturizer all over the body. Dry skin causes rashes. She can take food rich in vitamin E or vitamin E supplements for skin and heart health. To get rid of itching she can apply ointment hydrocortisone on areas affected. Taking antihistamine at bedtime will also help to get rid of itching and discomfort. She is advised to take Acetaminophen after food as she is febrile. Fever with rash could be indicative of herpes, scarlet fever, mononucleosis, etc. Get her examined and evaluated by a GP. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician