It sounds like you have some pretty bad allergies towards what's in your substrate. It could be anything from the sawdust itself, yeast, the gluten and other proteins in wheat, to contaminants found in any of the ingredients.
It's a common practice in the US to use herbicides before harvesting grain because it not only kills weeds in the field, but it causes the plants to produce more seeds as a last attempt to ensure survival. Some people are actually quite sensitive to the herbicides, and many people who are diagnosed as being sensitive to gluten are actually sensitive to the herbicide residues left in grain products. I wonder if this might be something you're reacting to?
