My understanding of allergies is that they are more or less immune responses to non-pathogenic substances. The definition on MedicineNet more or less agrees with this.
While I don't have any known allergies myself, I know people who do and they have been very vocal in telling me that they literally can't take even a bit of a substance. For example, even trace amounts of peanut dust or a bite of shellfish can send them straight into anaphylaxis and a trip to the emergency room.
My question is, if allergies are nothing more than an immune response, why don't people have allergic reactions to pathogenic substances that they have developed antibodies for? For example, considering the amount of SARS-CoV-2 circulating in my area combined with widespread vaccination for it, I would expect to see non-trivial numbers of people breaking out into hives, going into anaphylaxis, etc., upon entering a room filled with airborne coronavirus, but this doesn't actually seem to be happening. When I got my COVID-19 vaccine, I was not advised that I might now be allergic to the virus and should consider allergy medication if visiting someone likely to be infected.
For example, why don't I hear things like this regularly?
Hey, before I come into your house, I just wanted to let you know that I am highly allergic to Influenza type A H1N1, Influenza type B/Victoria, SARS-CoV-2 Delta, and several strains of Epstein-Barr common in the South Pacific. If anyone here is infected with any of them, I'm not likely to get infected per se but I might go into sudden anaphylaxis if they get into my lungs. If this happens, please use the epinephrine injector in my left pocket and call 911. Thanks!
To be clear, I know that the classic signs of an upper respiratory infection (cough, runny nose, etc.) are generally caused by the body's immune response. My concern here is that these are generally much milder and have a much more delayed onset than typical allergic reactions, which are often immediate and life-threatening (rather than taking days to develop like a typical cold or flu). People who are allergic to peanuts often carry emergency epinephrine injectors and let their friends know that they have them and might need them. People who have recovered from a viral infection that is still believed to be circulating in the community don't. My question is why?
If there are viruses or other pathogenic organisms that do commonly generate allergic reactions (e.g. persons who are immune need to stay away from sick people so they don't have an allergy flare-up if some of the virus gets in them), then that's an answer.