Hello,
Such type of itching can be due to thyroid problem or allergic reaction to dust. Treatment includes avoidance of allergen. To reduce dust in your home, remove drapes, feather pillows, upholstered furniture, non-washable comforters and soft toys. Replace carpets with linoleum or wood. Vacuum soft furniture and curtains as well as floor Wash carpets and upholstery with special cleaners, such as benzyl benzoate or tannic acid spray. Wash all bedding in hot water (hotter than 130°F) every 7 to 10 days. Don't use mattress pads. Cover mattress and pillows with plastic covers. Lower the humidity in your home.
You can use antihistaminics like benadryl, zyrtec, decongestants and corticosteroids. In severe cases, Immunotherapy is advised. Also ask him to get his TSH levels and thyroid hormones done.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
How long has he had the problem and how often does it occur? Does he get a thick skin like rash after scratching ?
He could have many things--an allergy, poison ivy, side effect of thyroid disorder. Calamine lotion should relieve the itching until he can see the dermatologist. I don't know of anyone who has ever had a negative side effect of calamine lotion, so either ask your dad if he's ever used calamine lotion or ask the pharmacist if it is safe to use on your dad.