I'm allergic and have had a pretty bad reaction.
I was making deliveries in FL for a summer job and no one was home at one house but there was a swarm of bees / wasps or something and one stung me on the lip. At first I thought it a minor hassle but then noticed that my arms were turning red, when my vision started to blur I decided I should do something. Went to the next house on the list (not familiar at all with the town) and the lady that lived there ended up taking me to the hospital. I got there within 30 mins of being stung but I was covered with hives head to foot and couldn't talk enough to tell them my name. Needless to say I didn't wait for attention in the ER, they took me back and gave me several shots. I remember them remarking that they hadn't had anyone this bad in awhile

and watching for the red to ease on my legs. Ended up staying in the hospital overnight and released the next morning. At that time the Dr said I could have as little as 3min before a bite would kill me if I was stung again. Thankfully it's been more than 20yrs and I haven't been stung since. I've had reactions to ants but only the hives.
I do carry an epipen but I'm bad about having it current, I talked to an allergist once about shots but at that time they were pretty new and the long term results weren't known. Also because of the severity of the allergy I'd have to stay at the Dr office for 3 hours every time I got a shot. Decided to take my chances. It maybe very different now.
I've also been told (by another allergist) that because it was so long ago and I haven't been stung the next reaction probably wouldn't be too bad. The danger would be multiple stings or getting stung and then again not long after that. Something about the antibodies ? becoming dormant.
I was also stung as a child but didn't think anything of the fact that I swelled immediately and more than anyone else. Just didn't realize about the allergy and that it would get worse.