I have no doubt that allergies are the unpleasant side effect of industrialization. I had the pleasure, from age 6-14, to grow up right next to a major chemical factory built into a valley. It was completely normal for us, on a calm day when the winds did not sweep the valley to breath in air full of ammonia. I clearly remember how it was suffocating while we were waiting for the bus in the morning. The air was completely YELLOW above you. Most of my friends, my sister, etc all have some sort of allergies or respiratory problems.