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

I’d like to know this because I have a large wooded property I work on and have developed allergies to several plants in recent years. I spent years and years working in and around these plants with no issue and now coming into contact with any one them is awful. I’m 59.