Your son is having urticaria
There may be many causes.
Food,dust,insects,cold,heat,physical and so on...
The culprit should be detected and removed...
Then he might feel better.
Continue antihistaminics for long time.
If it is severe, you may give short course of steroids
He should be consulted by dermatologist
I hope you got my answer.
Dr. Ilyas Patel MD