I suffered from allergic rhinitis for so many years (and recurring sinus infections) until I found out that the cure for me was Vitamin C. Normally, I drink freshly squeezed orange juice of grapefruit juice (be careful if you are taking prescription pills). However, it is not convenient or possible to drink fresh squeezed juices every day. When I feel that my nose is getting stuffed I take couple Vitamin C pills and I feel better the next day. Or if I have a horrible sinus Headache I take 3 or 4 pills at night and the next day I woke up with no Headache. This vitamin has helped me a lot during our January trip to Switzerland. After a day in the Alps we took some and next day we felt great. My husband thinks Quercetin also helps him so he takes Quecetin pills with Vitamin C. I suggested friends who were suffering from allergies and they reported that it helps them as well