IMO, chemicals do matter. Toxic chemicals cause and contribute to PN. The flame retardants and formaldehyde in many are cumulative. Why put the extra burden on your body if you can avoid it/afford it.

A client of mine recently purchased a mattress for her son and the next morning, he awoke with swollen hands and feet and a rash on his body. Any time he got near it, he started to react it. She thinks that since it was wrapped in plastic, it had a lot of out-gassing going on.

A new mattress may not resolve your problem but it will not contribute to it either, making it worse. Anything you can do to minimize the toxic overload in your body, the better.