I'm allergic to bee stings.
And I have been stung a lot. Ones and twos here and there, and a couple of times when I was stung hundreds of times at once. When I was young it was no big deal, and little or no reaction. But in my early 20's I knocked over a beehive with a tractor. I tried driving the tractor away before shutting it down and dismounting, but that proved to be a bad move, as tractors don't move very fast, so I shut it down and bailed, heading for a water hose. Got the bees away from me by hosing off, then went into the house.
I started to go into shock, and the swelling started. I called the doctor, they said call an ambulance. I hopped in the car and drove to their office, as it was only a few blocks away. They gave me a shot of something, and put me in an exam room. A nurse plucked hundreds of stingers from my scalp, neck, ears and arms, then left me alone. After a bit they came in, took my vitals, and gave me a shot of something else. About an hour later the doctor came in, examined me, asked how I was, and if I knew I was allergic to bee venom. I related my life's experiences and he prescribed an epi-pen, telling me that I will always need to have a fresh one nearby, if I ever get stung again I would need to use it immediately. He also said I should have called the ambulance, that treatment been delayed much longer he would not have been talking to me then.
He then asked the nurse to give me another injection, and said goodbye.
So I got an epi-pen, and replace it every two years.
I've been stung by yellow-jackets a couple of times recently, but didn't have the extreme reaction I did with the honeybees. Yellow-jackets don't loose their stinger, and can sting repeatedly. Each time it has only been one individual doing the stinging, and each time I had several stings. I promptly took benadryl, and the swelling and reaction was fairly mild, so I didn't feel the need to use the epi-pen, or see a doctor.