I've taken benadryl several times before bed. Once to relieve allergies enough to go to sleep (when I spent the week at my girlfriend's house, something in their house was absolutely making my sinuses go crazy, never had anything like that happen before), and sometimes just to make me drowsy. Doctors give trusted answers on uses, effects, side-effects, and cautions: Dr. Hoepfner on benadryl before surgery: Either the recommended amount based on weight through the directions on the box or following your doctors recommendations if the recommended dose they made is higher. It may seem strange to take a medication for allergies during recovery after surgery, but there are many uses for this drug, some of which are very useful in the hours and days following surgery. Diphenhydramine is frequently given before and after surgery to prevent a very common complication of surgery: nausea and vomiting. benadryl (diphenhydramine) Should be fine, but would rather take 25mg if you have not taken it before regularly, as you may have a hard time waking up the next day. Learn to Sleep Better. The three cornerstones to a healthy life are diet, exercise and sleep. Sleep is the easiest to fix! Read about the latest sleep research and get advice to help you learn how to get the best night’s rest possible. Tylenol pm is not the same as plain Tylenol. When in doubt check with your ob-gyn always. You may want to try something like camamille tea just before bed and place a lavendar scented satchet under your pillow. Benadryl doesn’t affect your liver like alcohol does. But both drugs work on your central nervous system (CNS), which is made up of your brain and spinal cord. Benadryl and Claritin basic facts. Benadryl is a Brand name for antihistamine drug that contains diphenhydramine as an active ingredient. This substance reduces the effects of natural histamine during allergic reaction in the body. I take it because for years I've had inner ear fluid build-up. One Benadryl per night seems to be enough to keep the ears dry & the resulting nausea at bay. I was told to just take a benadryl at night since it was cheaper than buying the sleeping pill versions. I was told it was the best type of sleeping pill to take as it is helpful to your system, non addictive and if you have allergies it will help with that too.