it is usually not necessary to take two antihistamines on the same day but there are exceptions. claritin is given once per day but depending on the time you took it it could be wearing off around bedtime for instance. since benadryl can be very sedatiing and only lasts for about 4 hours a person could take it even though the claritin was still on-board.
can you take benadryl and claritin together?