benadryl (diphenhydramine) lasts about four hours so you can use certirizine anytime after four hours.
our 6yo had 1 dose of benadryl in the earlier (did not work) how many hours must we wait to give him 5mg cetirizine? . for two days prior we gave him single doses of claritin which did not work well. we tried one does of benadryl around lunch today and after a day outside his allergies are terrible at bedtime. would like to try certirizine (childrens). thanks in advance