What can I give my rat to help with congestion and sneezing?

My rat millie looked sick yesterday. Eyes half open, slight red mucus, fluffed up, a lil slow. So I took her out and let her sleep in another cage alone, fed and watered her. She got energetic at her usual time and I let her out to play. Right now she is the same with the exception of sneezing and a whistle in her nose. What can I give her to help with the nose and combat sneezing?