Caroline,
If you have an aromatherapy diffuser, you could try essential oils to see if that's helpful.

The old staple here being eucalyptus or tea tree although companies now sell beautiful blends that can aid breathing. e.g. eucalyptus, mint, myrtle. That's one blend I have and it's called "breathe easier". You'd probably need to play around with them a bit just in case they're too strong and make the situation worse.

A lot of oils are toxic to pets so don't use those ones if you have pets inside.

p.s. I read somewhere about normal saline nose sprays. Might be worth looking into as well.