allergic reactions
"I take one before bed which keeps me breathing easily during the night despite my allergies.  It also helps me get to sleep and stay asleep.  The active ingredient, dyphenhydramine HCL, you will find is the main ingredient in quite a few over the counter sleep medications so that should tell us something.  And Benadryl or a generic drugstore brand are cheaper and just as effective.  Have been taking this for over 20 years and have no side effects"