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
Because they’re different immune responses.
Allergies are from Immunoglobulin E and involve Eosinophil white blood cells. These cells contain a lot of histamines, which cause the unique symptoms.
Colds/viruses invoke a lot of different cells, but they dont invoke Eosinophils. Many other types of white cells react and release interleukins. These have a wide range of effects, from recruiting more white blood cells, starting the Immunoglobulin M and Immunoglobulin G responses (G provides future immunity), causing inflammation, fever etc.
The “boredom” is true, Eosinophils are evolved to attack parasites. And in our clean world, they get bored and start getting sensitized to weird things. Interestingly, one of the treatments for severe allergies is introducing parasitic antigens.
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