Benadryl is a medication that is not discussed in most first aid level courses; without specific training, I wouldn't carry it. If I did, it would be for personal use, and not for treatment of others
My Wilderness First Responder class included a discussion of Benadryl. Also, it's included in my protocols (written by Wilderness Medical Associates) for treatment of anaphylaxis. So for me, not only is Benadryl within my scope of practice, it's part of my standard of care (along with epi), so I carry it.
Interestingly, when I ride with my college's EMS, Benadryl is beyond our scope of practice, so we cannot use it. It's weird to think that I have over-the-counter meds in my personal first aid kit that I can't use and don't have access to when I'm riding an ambulance.
At some point I'll probably post a list of what's in my first aid kit.