I might have given a double dose to my son. iterax 2mg/ml bottle. my son is 6 years old and weigh 20 kgs. i gave 2 teaspoons for hives?

Can cause drowsiness: This medication is an antihistamine. It can cause drowsiness, sedation. Probably not a tremendously big deal, be more carefull going forwards.

Ok but...: I presume that you meant Atarax (hydroxyzine) and not iterax. Even at higher doses , it would be ok and in fact your son may well need doubling the dose to control his hives. This is not to say that i endorse using a dose above a manufacturer's recommendation without a doctor's supervision.