Originally Posted by Blackcat31:
LOL! I googled "Bendryl before vaccines" and all I got was tons of dog forums saying that it helps ease the anxiety and possible allergic reactions dogs commonly have before immunizations... 
It might be a Mississippi thing but it sounds as though it's a canine thing too! 
According to my vets and the reseach I've personally done, giving a dog Benadryl pre-vaccination is pretty ill advised as well as being counter productive. One of my dogs gets a giant dose of of dexamethasone before his vaccines only because he's severely allergic to the preservatives in them....but like the active ingredient in Benadryl it's an immunosuppressant.....which can to an extent, if not entirely, lessen the efficacy of the vaccination.
Same goes for children. Giving them Benadryl beforehand could almost completely defeat the purpose of giving the shots at all.
I think it's entirely overused and abused by many people on a daily basis. I'd go so far as to agree with Nan that they, along with childrens anti-inflammitories, should become monitored prescrption medications just like cold remedies with pseudoepedrine in them are. People
today are a combination of overly paranoid (using them for everything), overly confident (thinking they are doctors capable of self diagnosis and treatment) or are just plain stupid, not taking the time to research and administer them properly.
Living beings are dying everyday. It's a freaking epidemic.
It is NOT well enough studied for use as a sedative in ANY circumstance, doc advised or not.