It's because the world is low-oxygen. What about living where it is a densely wooded region? If mold is such a factor where you live, best to find a good balance between dry-arid (low mold) and wet-tropical (higher mold). When there is more oxygen, mold and parasites (dark, wet low-oxygen opportunists) die off FAST! You should run and run up hills or inclines to incorporate the UPPER LUNGS. When you sweat and itch at the hairline this is your lungs strengthening. Which means better oxygen-utilization is occurring, which means better defense against mold. OXYGEN INJECTIONS are your best defense. Get the oxygen even if it hurts, forget pain and think of pain as more oxygen. Hope that helps, I know it's very common-sensical...