Tom, I've been a lurker for a long time (and love your writing) but I had an experience today that I hope I may ask you or your readers about, relating to this post. I called out an ambulance for what I thought was a severe allergic reaction, and I am worried that I did waste their time but I really don't know how to tell when it's so bad that the ambulance is needed. Basically I am pretty sure I am allergic to peanuts, I had a very severe reaction before while in the US (that I stupidly didn't get tested). I ate something today that might have contained them, which I noticed from my hear rate becoming rapid, my throat getting tighter and feeling very dizzy. I called 999 and asked the operator if she thought on the basis of this I needed an ambulance because I didn't want to waste resources; while talking to her it also got quite a bit worse and she sent an ambulance. By the time they got here I was still very dizzy but able to speak and my heart rate went down. My functions turned out to be normal. My question is, how do I know indeed when it is serious enough to call an ambulance? I am feeling so embarrassed that I seem to have called them out over nothing.