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Itching all over the body can be due to many causes, especially allergy
to foods or medications or any infections, viral or fungal.
If its severe and you dont know the cause , its best to consult your physician who can examine her, take detailed history and provide exact diagnosis and treatment in the form of anti histaminics anti allergen medications like cetrizine
.he may also advice you local calamine
lotion application for soothing relief.if she has any other symptom like rash, fever or breathing difficulty or swelling of body them take consult your doctor immediately.if it has been since many days with no other symptoms then consult a dermatologist