In 2004, I bought a Whirlpool water heater from Lowes. It was their top of the line with the lowest energy costs and lifetime warrantee and it uses a high density fiberglass insulation. It is actually made by US/Craftmaster Water Heater Company in Johnson City, TN.

I do agree with others that your problem may not be with your water heater, it could be with the plumbing materials or the water itself. Also the house could be insulated with a foam insulation. Even fiberglass insulation is now coated with some type of material to make it less brittle. For people with certain allergies, that is a no win situation, when the fiberglass breaks up into dust, it is an allergen, but the coating that prevents this will off gas an allergen.

The house you are in might also have a mold problem that has not been detected. I know a couple of people like you who have severe allergies. It is hard for them to move once they get a house "cleaned up" enough for them to live in, and they don't have to move every six months.