As opposed to being born that way, how does a person become allergic to nuts? Can it be from eating too many of them?

I don’t think people become allergic to nuts by eating too many nuts.

People aren’t really born allergic to anything, per se. Allergies do develop over time, and require repeated exposures. However, the degree of exposure to specific allergens (i.e. nuts) does not correlate with their development. There remains a lot of controversy about nut allergies, specifically regarding how early children should be fed nuts.

This describes the three ways one can become allergic to something:
The Development of Allergies

Very unlikely. It might have to do with the amount and nature of chemicals we are exposed to as children and adults. Growing up on farms seem to help avoid certain allergies.

I am highly allergic to all nuts (insert lame joke i’ve heard a million times) the worst one is pistachios for me.

As a child I ate peanut butter and jelly sandwiches a LOT. It was my most favorite food according to my mother. Then one day she gave me a sandwich, walked in the other room, came back and I was covered in hives. Ive been allergic since.

I am lucky however in the way my allergies work, I generally have 20–30min before it hits me bad so I have a grace period to get some sort of medicine into me before i start vomiting and my throat closes. Thankfully im not like the people who can kiss someone who ate nuts 4 hours earlier and then drop dead.