There are a few things. Anything with a sore throat find a health food store or an herbalist who has Frankincense (the actual little balls of sap, they might be labeled "frankincense tears"). Drop a few of the tears in the bottom of a coffee cup and pour boiling water over it. Sip it as soon as it's cool enough to stand and breathe in the steam. Myrrh is great for anything respiratory and can be taken exactly the same way, though I find it very bitter and unpalatable. I take powdered myrrh in capsule form instead. Mullein leaf is again good for anything respiratory, I harvest it wild and dry it to use all year long. Similarly bitter and gross but it helps. If you have a diffuser, diffusing essential oils can be really good for keeping your sinuses open. Tea tree oil works really well for most people, I am unfortunately slightly allergic so I use peppermint and a few other things I can't remember the names of at the moment. A couple of brands have a mixture with a name like "breathe easy" and those contain the stuff I'm talking about. Don't diffuse citrus oils in an enclosed space with animals, especially cats. But I find that keeping a diffuser running beside the bed while I sleep helps keep my sinuses open while I'm sick.
