Salli,
Only one of my daughters takes a daily allergy med. When she was younger she didn't show signs of allergies. But about a year or so ago, they kicked in. At first I wasn't sure that it was allergies, just thought the symptoms were more like that of a cold. But the soon became obvious...red, itchy, watery eyes and very runny nose. She was miserable.
So we had her allergy tested this spring. She is allergic to practically every tree and mold that they tested her for. So, we now give her an allergy tablet every day because she suffers from them so badly. My younger daughter was also tested for allergies, and only is mildly allergic to one type of mold, so therefore doesn't need daily allergy med.
I know that your reaction to different types of allergens can change over time. So my younger one could start to have reactions when she is older, but right now she does fine.
One problem that I have noticed with the allergies and my older daughter is that all that runny nose and stuff seems to go to the lungs before it's all said and done if not treated properly. Maybe it's also the inflammation in the lungs due to the allergen. I am not sure, but I do know that Saskuska has a lot about it on her blog, so maybe you can go there for more answers.