hi welcome to HCM
-hi i had gone through your query and understand your concerns. i would come up with the possibility of
ALLERGY is the underlying cause for your son sufferings.
-allergy leads to URTICARIA
possible cause of allergy;
--physical factors like heat,
cold,sun,exertion,pressure,vibrations.
-food and food additives
-Drugs
-insect bites
-intestinal worms are some triggering factors for the development of allergy
treatment option;
i advise you taking
Homeopathic medicines gives safe and permanent cure for your son allergic complaints
consult your local homeopathic physician for correct diagnosis of the case and remedy to fit his complaints
I hope this is helpful for you, thank you