Each day into this glass goes different allergens, cat or dog dander, dust mites, dust, particulates, mold spores, VOCs, diesel fumes, smoke, all manner of allergens. The glass starts to get full. Once this happens the individual gets sick. One can only take so much. The point of all this, is that we need to limit the total amount of allergens we come in contact with.
Avoidance is the real key with allergy.
It's all positive. There are of course other benefits to this besides simple avoidance. Female trees in one's own yard will attract and then trap incoming airborne pollen from males of their own species. We could easily think of female trees as our first line of defense. It is, to me at least, quite incredible that the female stigmas, of wind-pollinated dioecious and monoecious species, produce a positive electrical impulse, and that airborne pollen is itself negative.