is a steroid
,its main side effect are nausea,weight gain and many a times immunosuppression
Continue with pan40 and defcort,Your son is most probably suffering from gastoebtrities its common in his age group,you should administer him plenty of fluids and oral rehydration solution available nearby you.. He will get relief by own.
If the problem persist you can take a combination of oflaxacin and ornidazole
it will help..but you have not mention the weight..and he is on steroid I.e defcort so.. I recommend you to take an pediatric opinion before administering the tablets