Yes, all allergies develop from repeated exposure to the allergen, but not all things you're repeatedly exposed to end up triggering allergies.
I've mentioned in a couple posts that I have a confirmed allergy to apples and peaches. I get severe hives and my throat closes up just like someone who's allergic to bee stings. I have to get to an emergency room right away or I'll die of suffocation. And I'd always eaten apples all my life with no problem. The allergist explained that each exposure sensitizes the body a little more until BOOM, you have an allergy! Trouble is, there's no way to predict what you might become allergic to. One of many reasons for a balanced diet with a variety of foods and moderation in all things.
PS. Yeah, it was pretty scary when it happened! Now I'm like Snow White and think of apples as poison!!