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Based on the information provided by you, there are two possibilities- Seborrhoeic dermatitis
Based on the description given, your child is likely to be having seborrhoeic dermatitis. As it is recurrent , the primary cause is to be treated. The primary cause is Seborrhoea
( Dandruff). In case if your child has dandruff of scalp the treating it shall help your child. The reason for me going in favor this diagnosis is that the shoulder girdle is the area where the dandruff tend to fall . Using Ketoconazole
shampoo twice a week will get rid of dandruff. Applying lotions containing lactocalamine or liquid paraffin
on the effected skin will relieve he itching and irritation. Along with taking levo cetrizine 5mg will relieve the itching.
Coming to the second possibility of Urticaria, it could be due to allergy or insect bite. In that case the treatment given by your doctor would have worked.
Hope you got the solution you were looking for.