It literally burns to breathe in my home

[Nichole Dillabough]

I just recently moved into the historic district of Colorado Springs, and it's so great! I love the character of the area. However, recently whenever I am home, my allergies are making life miserable. Since it is an older home, I am afraid of what is lurking in the furnace/vents/walls. It literally burns my throat to breathe when I'm in the house. I've lost my voice twice already, and have spent a lot of money on nasal spray and antihistamines to no avail.
What are my rights, as a renter, to have my landlord have something done about this? He is a first time landlord, and I am afraid he will turn me down since it will probably cost a lot to have done. I would just like to have some backing when I walk in to this conversation.

Thanks so much in advance,
-N