When we experience an allergic reaction, it's because our bodies are exposed to things called allergens (i.e. pollen, mold, pet dander) that our bodies mistakenly recognize as foreign. Because our bodies are crazy smart, they produce immune or inflammatory reactions in order to "fight off" these foreign invaders to help keep us alive and well.
It's common for people to become less sensitive to allergens as they age. It has also been shown that, when a person experiences a very mild allergic reaction or immune response, repeated exposure to the allergen may cause a decrease in that person's sensitivity over time. In other words, the more you are exposed to something (in moderation), the less likely your body is to react to it in an adverse way (which you can thank your memory cells for).
By consuming honey that has been made locally, you are actually consuming the local pollen and, therefore, are preparing your body for the "threat" (allergen) that it may later encounter.
Pretty cool, right? You can get local honey from a farmer's market, produce stand or sometimes even your local grocery store.