Born and raised a NZ farmers son I have been allergic (pollen) and suffered from asthma (allergic not chronic) all my life. I grew up surrounded by dirty dogs and more sheep and cattle than most people will ever see in a whole lifetime.
Did the fact that precautions were not taken with farm chemicals back then have something to do with the allergy. I have been exposed to DDT, pesticides, feretilizers, you name it.
So OK maybe this works in a city environnement with kids that live in a modern hyper clean envirronment and who eat agro-industry cr@p er sorry food. Didn't work for this farmers son.