If allergies are just your immune system going on alert for no good reason, why does it feel so different from your immune system going off for a good reason e.g a cold?

Question

If allergies are basically a pure immune response – no actual pathogen, just your body mistaking something harmless for a pathogen and freaking out – why does getting hayfever have distinct symptoms that most illnesses don’t have? Why does my immune system being set off because of harmless grass seed and pet dander give me itchy eyes and hives, but when it’s set off by a real virus it doesn’t do either of those things? On its face, shouldn’t being sick feel like “all the symptoms you get during an allergic reaction + whatever symptoms are caused by the actual harm the pathogen is doing”?

In: Biology

Answer 1

The same reason that your immune system response for a cold is different than your immune system response to a bacterial infection in a wound. Different pathogens cause different immune reactions based on what your immune system thinks it needs to do to eliminate the threat.