Thank you so much for doing this! I have plenty of anaphylactic food allergies myself, which is actually one of the reasons I got into overlanding in the first place, as I can bring all the food I need to bring, with me! I carry a couple Epi's in my first-aid kit and have had to use them a few times - not on myself, but on others who didn't know they were allergic to bees and certain plants.
I wrote my thesis on food allergies in young adults. A lot of people think it's a problem that just affects kids, which it isn't. One thing that stuck with me through the research was how common and varied allergies are. About 7% of people are allergic to something, and that could be anything. It's often not something you grow out of, either.
If there are mild symptoms then Pepcid might help but in the PO form the dose has to be much larger than normal due to first pass metabolism in the liver. I wouldn’t rely on it in the back country. If you only have Benadryl and Pepcid then go for it and use both.