Could my environment make me more likely to develop allergies?

There's more to developing allergies than just heredity. The things that you become allergic to are also based on when you're exposed to a substance and how much of it you're exposed to.

Let's say, for example, that you have a tendency to be allergic to mold spores. You may have no allergy symptoms when you are living all alone in your spic 'n' span apartment complex. Then a new roommate moves in, bringing along a veritable jungle of houseplants, an smelly old mattress, and a humidifier (to keep her skin moist). Soon after her arrival, you become a symphony of snorts and sneezes. What happened? You'd endured a certain small amount of exposure to mold spores with no problem, but once the scales were tipped by the hefty onslaught of your roommate's mold-bearing possessions, your immune system kicked itself into high gear.