 [ Symptoms ] is it ok for my 5 year old to take benadryl on a daily basis he has really severe outdoor allergies and i was told that benadryl at night and zyrtec in the morning is ok to do can you please confirm yes or no [ Disease ] zyrtec lasts 24 hours so usually benadryl is not needed it is safe to give it at night even if he is on zyrtec but this first generation antihistamine can interfer with restful dream state sleeping