I also suffer from it but thank God it is acute, not chronic..yet. I found this once when I wake up with a really strong headache and sinus swelling. I didn't know how to relieve internal sinus swelling alone, at home, since I am always seeking for some natural treatments, but there was no help in this for me. Then my doctor told me that homeopathic medicines can be of great help in the treatment of Sinusitis. The natural Homeopathic mode of treatment aims at rebuilding the body’s immunity to Sinusitis. There are several of them, but I suggest you consult someone to see which one fits you the most.
However, having said that, here is what cured my sinusitis.
I cured my long-standing chronic debilitating sinusitis with pineapple. I eat a small amount every day--sometimes just as a slice sometimes in a fruit smoothie. Pineapple won't work for those who are allergic. For those who merely dislike the flavor you can buy bromelain--though I think food sources of enzymes are usually superior in part because some of these enzymes supplement manufacturers add so much sugar. Besides mother nature is more trustworthy than a processing plant.
I make smoothies of pineapple and other fruit--no dairy through--the other fruit can disguise the flavor of pineapple--if you despise its flavor--while pineapple when blended becomes foamy like milk and gives the smoothie a milkshake texture. Best if the fruit is organic and fresh--that is RAW.
The pineapple has to be fresh or raw. Canned, cooked, frozen won't do. Canning, cooking, freezing, processing destroys the enzyme bromelain which is the natural anti-inflammatory which helps reduce the inflammation in the sinuses so they can drain. It is a protelytic enzyme which means that it breaks down proteins. One theory of inflammation is that it can be caused by circulating undigested proteins which the body cannot break down and carry away, but with the help of protelytic enzymes it can.
Don't eat too much, however. It breaks down protein and a symptom that it has gone to work on your body is sores at the corners of the mouth. Not that this should make you afraid. The irritation usually clears up in a day if you have gone overboard with your pineapple consumption. I generally eat about one 1/2-3/4 inch slice of pineapple a day and no more. See what works for you by starting small and working up.
By the way, this may not work for everyone, though there is reason to believe that it can for a great many more than are being treated at the moment--see article at link below. Those with candida may wonder if it is wise idea to eat pineapple and may want to try the tablet form of bromelain, but make sure the tablet contains significant amounts and does not contain sugar, which some manufacturers add to make the tablets more tasty and chewable. I can't vouch for the effectiveness of this as I prefer pineapple in its raw state.
Attached is a link to an article about bromelain.
BTW, researches are looking at bromelain as a cure for cancer. Bromelain dissolves fibrin which often protects the cancer from detection by the body's immune system. (If you read the above article you will learn about fibrin and sinusitis.) Even if the immune system is capable of combating cancer, it cannot find the cancer under the fibrin. But pineapple breaks down the fibrin allowing the body to detect the cancer and deal with it. There is some research that indicates that bromelain may be able to cure cervical cancer.
Interestingly many years ago while Marie Curie was exploring radium, there was a doctor, Dr. Beard, who was experimenting with enzymes to cure cancer. He had marvelous success, but when others tried to repeat his experiments they failed because they were using low quality enzymes. So they poo-pooed his research. Thus cancer research and attempts at cures took an altogether different path, one which regrettably has not been all that successful considering how many years that our medical system has been devoted to it. Under our noses on our plates may be the cure in the enzymes that our in our foods. But we have to not cook and process them out of our foods for them to be effective.
One other item of interest. Pineapple has cured another of my family of Yellow Fever--but it was the vitamin C and the pineapple was canned. Years ago my father was about to go off to the pacific during WWII. They vaccinated him and in the vaccine was a live virus. He ended up with Yellow Fever and confined to a hospital bed. He asked the doctor what he could do for it and the doctor said vitamin C and so my father began drinking pineapple juice and recovered. The vaccination saved his life. Had he gone with the ship he was supposed to go on no doubt he would have drowned in the South Pacific when that ship sunk. My father did not know how to swim.