Its a really good question, and I won't pretend to be able to give you an authoritative answer. But my non-expert answer would go like this.
I think the answer is probably both yes and no. Yes for people who have an allergic predisposition. People who have true allergies have a condition called atopy, which causes their immune system to go into overdrive and produce too much of something called IgE when they are exposed to everyday substances that don't faze most people. I think about 20% of the population has this characteristic.
Life as an atopic is unpredictable. I have become allergic to things in adulthood that I was not allergic to as a child, and vice-versa.
OTOH, it's hard for me to imagine how a person who is not atopic would one day go into anaphylactic shock from peanuts, but like I said, I am not an expert.
I have gradually become allergic to more and more things over the last fifteen years (since adulthood). I just saw a Dr. two weeks ago for a tiny scratch that turned into a teeming mess of hives (second time this has happened in the last 18 months).
She told me it was a hyper-immune system response to an injury; usually seen only in some patients with allergies.
Both times this has happened, the initial response has been antibiotics (which obviously don't work); topical steroids cleared it up. Just thought I'd pass that along in case it ever happens to you!