they are both antihistamines. the zyrtec is purported to be a non-sedating antihistamine and diphenhydramine (benadryl) is a sedating antihistamine. when used as a sleep aid it can interfere with deep restful dream-like states so personally i am not a big fan of using it. if he wants to use both then just take the zyrtec in the morning (the diphenhydramine wears off in about 4 hours so it will be gone).
my husband wants to know if its ok to take zyrtec and his sleeping pill which contains diphenhydramine 50mg? . he uses an equate sleeping pill from wal-wart and the active ingredient is diphenhydramine 50mg. same as taking 2 benadryl's? we are confused by that.