While researching for my upcoming book, of Moose and Men, Ridgerunning in Maine's Hundred Mile Wilderness, I started wondering what the web says about accidental administration of adrenalin via an EpiPen. Among various links, I found this page Allergic Reactions and EpiPens
Last summer on the Gulf Hagas Trail, we had a nest of hornets that would get riled up when dogs were off leash. Turns out, the paper nest was at black lab nose level, right on the easier Pleasant River Tote Trail.
Once, while hiking the loop, I met a mom whose daughter had just been stung for the first time in her short life. Her father was allergic and after the incident, she headed straight back to the parking lot.
Of course, Benadryl can be purchased over the counter and carried as an emergency response to allergic reactions. Some use it after encountering poison ivy.
It doesn't always work and can cause drowsiness.
Untreated, a severe reaction can cause shock followed by death. If you know you're allergic to bee stings, carry a pen. You'll need a prescription, but its worth it.