I'm sorry to hear this. Poor fella. Good luck! Just a few thoughts. Maybe there is a pattern here? Could your husband accidently be bringing germs home with him from work? Highly unlikely, just thought I would mention it. Another thing I thought about was possible exposure to heavy metals, mold, or other poisonous reagents. Heavy metal exposure likely would occur either through exposure in the local top soil or the local water. Heavy metals are found in high numbers in older houses too. Old paint, insulation, countertops, masonery, etc, could contain lead among other things. Mold could come in contact with pets just about anywhere; basement, outdoors/rotting trees/stagnant water, water/food dishes or storage, etc. I hope this post doesn't come off as an accusation.....I just thought it might help find a cause. Good luck Viggo!