What causes your body to suddenly develop an allergic reaction to something later on in life that you weren’t allergic to before?

Question

i.e. how does ur body suddenly decide something is dangerous enough to warrant a reaction even tho it didnt cause it before

i might be using these tags wrong yeesh

In: 42

Answer 1

An allergic reaction is caused by our immune system.

When an invading pathogen gets into our bodies, like a cold or like Covid, our adaptive immune system will pull the pathogen apart and study its chemistry. It then develops a response such as antibodies that can bond to and destroy the pathogen. But the immune system isn’t perfect, and occasionally it makes mistakes.

We gain allergies when our immune system misinterprets something benign, like pollen or the shell of a peanut, for an invading pathogen. Then each time we encounter than thing, our immune system goes into overdrive trying to destroy it, and this overdrive is the allergic reaction.