Hi, welcome to the forum, itching seems secondary to allergy known as atopic dermatitis and also other strong possibility is irritant dermatitis. This condition can be associated with asthma. Remember if you have been exposed to any chemical (detergent, shampoo etc.) or new garments which might have caused irritant dermatitis. if it is present, Avoiding these situations is helpful for acute flares as well as for long-term management.
Other forms of treatment are use of anti histamines and corticosteroids against prescription will help to reduce itching of the skin as well as rash. you need to consult dermatologist without delay. Take care and regards.
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Blessings
Nikodicreta