I've probably had dozens of sinus infections. This is partially related to my genes; I got some good ones, but sinus problems and severe allergies run in my family. I ended up with both, with the result being a cycle of allergies triggering infections. In fact, I've got one now (receding thanks to Zithromax), which got me to thinking about what they were and what caused them.
First, its important to understand the anatomy of human sinus cavities. The term "sinus" is a general one meaning "pocket" or "cavity," but in this case refers to a number of air-filled spaces in the skull (shown in the diagram below).
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The frontal sinuses sit above the eyes, behind the forehead. The maxillary sinuses are behind the cheekbones, the ethmoid sinus is a small area within the ethmoid bone between the eyes, and the sphenoid sinus is in the sphenoid bone under the pituitary gland. The sinuses are linked, and are lined by mucous-producing goblet cells. Mucous, although considered "gross," is quite important in maintaining a clean and infection-free sinus. Air comes into the sinus passages through connecting passage-ways, and if any of these passages become blocked or narrowed, infection of the inner spaces can occur since the mucous inside can't drain out. For example, allergies can cause inflammation which would lead to narrowing of passages. 
The lining of the sinuses are covered in cilia, small hair-like protrusions into the air- and mucous-filled space and serve to move mucous (and the pollutants/debris/etc they catch out of the air). These cilia can be damaged by all sorts of things, from air pollution to cigarette smoke to a lack of humidity. Damaged cilia means stagnant mucous, and thats not a pleasant or healthy thing (easy infection target.)
A counter-intuitive piece of info is that a sinus infection (sinusitis) can be a follow-up to a viral infection. The virally-damaged tissue becomes vulnerable to bacterial infection (Haemophilus influenzae, Strepococcus pneumoniae, Moraxella catarrhalis, Staphylococcus aureus are most common). Other causes can be a fungal invasion, which are most often seen in immuno-compromised patients and can be quite serious if left unchecked.
A doctor (ENT, preferably) can tell you whether your sinus infection is caused by bacteria or a virus. If its bacterial in origin, there's a wide range of antibiotics out there, but my usual suspect is Zithromax as its fast, effective, and only consists of 4 pills to take. There's also a recent generic available, so cheaper is better too. Nasal irrigation with salt water is another way to prevent sinus infections and isn't nearly as bad as it sounds.
Have you ever used the corticosteroid drugs for allergies? I have had to use them for a while because of inabiity (or inadvisability) to use the regular decongestants found in OTC allergy/cold medications. I have found great relief of my persistent congestion. As far as I have found, there seems to be little risk for long term use, although intermittent use might be better overall.
Shelly,
Thanks for 'timely' info about sinus infection as the season is upon us, and the anatomical daigram with text descriptions on sinus is comprehensive and very well delivered. Here I add my own sinus problem, which is not originated by infection, but by seasonal allergic Hay Fever. The symptoms include nearly all you brought out, especially the sinus congestion, fever, and headaches. As soon as I notice the sign, I take ConTac, but in my case it takes usually an entire week until I feel I am back to my former self. Keep inform us, and thank you!
Mark, I wonder if your doctor was the one who suggested corticosteroids, and was it a last-ditch attempt to get your symptoms under control? Because honestly, what you describe can be quite dangerous, as long-term use of corticosteroids leads to Cushings syndrome. I have been on them before (Prednisone), but only pre-sinus surgery and only for as short a time as possible (1-2 months max). If there's one over-arching theme of my doctor's feelings about them, its get me off them ASAP.
Shelley, I was as concerned about their use as you, since seeing my father's response to long-term use of Prednisone to ameliorate symptoms of a progressive lung disease. As an older male, I have certain limitations on certain medications -- regular decongestants are usually specifically not recommended for people with BPH because they increase the symptoms. That left me without many choices. My doctor did, indeed, prescribe them. I questioned him about their use but he said they are not taken up systemically. I read the insert and did some online research, and it seems that the steroids in these (Flonase and Nosonex) do appear not to be taken up systemically. They are applied by nasal spray and even (as reported anyway) any that is swallowed ends up being essentially undetectable. They haven't been out long enough for really long-term studies, but what I have seen indicates that use for about a year appears not to cause problems. In any case, I do not use them regularly. Although they say that the greatest effect takes about a week or so, I get almost immediate relief when I use either, and sometimes at a lower-than-recommended dose. I am still somewhat concerned about using these for the long term, so I use them as sparingly as I can.
This is partially related to my genes; I got some good ones....
I'll say!
(heh heh)
More seriously, nasal lavage helps a *lot*. I've got my own problems with frequent sinus infections, a combination of normal variation and having had my nose broken six times, and this makes a *big* difference.
Oh, and you meant "vulnerable" -- "venerable" is what I am.
Also, if you've had a history to chronic sinus infections, you should consider a 30 day run of Augmentin; it's likely your zpacks are now just reducing the infection to a subclinical level.
Have you guys tried scuba diving? I found it was an effective (if painful) way to learn to increase air flow into and out of sinuses, thus making them less likely to block up.
Just be careful- diving before you master equalization can cause damage.
Irrigation may help:
At least twice a year for many years, I'd get a cold or flu that would resolve into a series of sinus infections lasting months. Two years ago, I started irrigating with a hypertonic solution of half salt and half baking soda in water. (I started with a commercial prep called NasoPur, and then made my own mixture after I ran out of the salt packets. I still use the NasoPur applicator.)
Irrigation simply means putting the solution in one nostril and letting it run out the other nostril. Sounds weird, but I haven't had my sinus infections since I began irrigating. Maybe it's woo, but I'm goingn to keep on doing it.
Jon, its definitely *not* woo. Pretty much every Oto doctor I've had has suggested it. I was part of a clinical trial for a pre-mixed salt irrigation system (NeilMed--it was just a squeeze bottle, but worked great). It made a huge difference, I'm just lazy about keeping it up after the trial.
Shelley: I didn't realize it was so mainstream. I wonder if you're also a fellow airplane sufferer. I travel a lot and irrigation seems also to have decreased the ear pain/blockage I experience during descent and the few days following. (Though I wonder if those baggage inspectors are have fits trying to identify the bag of white powder in my suitcase).
Shelley,
How do you know you weren't on the placebo?
I used the NeilMed, but it was a pain in the ass doing the mixing (find the distilled water, add the salts packet, warm the bottle....) "Simply Saline" makes a pressure can of saline that is a lot easier going.
It got so bad that I was thinking about just having my sinuses removed. Figuring out how to *remove* something that's basically a hole anyway is left as an exercise.
I seem to be doomed to make double comments this weekend. Anyway, I'm not clear how Mark is getting his steroids, but the risks of nasal steroids are actually very small --- the doses are small and there is a very small systemic dose. Here's an opinion paper that says they're generally considered safe.
Charlie, I am getting my steroids by a nasal spray applicator. The research I did indicates what you say, that the risks appear small and there is very little systemic dose (undetectable, one source said, using normal methods, at least in the blood). However, there are no long-term studies, since they have not been in general use for very long.
Another fan of saline nasal irrigation here; discovered that about five years ago. Works.
When I have a runny nose, another trick (that helps live with the, er, consequences of using the saline irrigation) is sleeping face down; the drip goes down and out instead of back and in. Far less nasty coughing at the end of a cold, doing this.
Doable either by just sleeping on the side with pillows arranged so the nose points steeply down, or supporting the forehead with a convenient chair and pillow, or using a massage table with an oval hole in it designed for that position.
The accumulation this way is, er, measurable. There's a science project -- weigh the bucket every morning. All _that_ didn't go into my lungs overnight? Ewwwwww.
Of course, I may have fewer and shorter colds just from increasing age and accumulated immunity to the range of cold viruses. The technique does work for younger friends who've tried these methods too.
I have a question? I had a sinus infection & i'm still on antibiotics. I feel so much better. But for the past 4 days around 11 am I start geeting a lot of sinus pressure, to the point that my gums hurt. It last about three hours and almost brings me to tears. Have you ever heard of this?
I am on week 3 of a combination of bronchitis and a sinus infection. Every night, about one hour after falling asleep, i wake up cholking violently on the thick mucus that has dripped out of my sinuses. And I do mean violently! My airway is in a spasm, I can't breathe, and I literally have to roar and scream to clear my throat of the mucus. This generally happens two or three times a night, and needless to say I don't get any quality sleep. I've been to the emergency room three times and my doctor twice. I've been on z-pack, Duratuss, a short course of prednisone, and an Albuterol inhaler. Now I'm on more Prednisone, Levaquin, and an elixir of promethazine and codeine. I've tried sleeping in every position imaginable. While physically I feel somewhat better, the nocturnal drainage and the resulting crises are frightening and exhausting. I got a neti pot four days ago and have been irrigating several times a day and in the middle of the night, but it hasn't made a difference yet. I feel like the health care professionals I've dealt with aren't taking this seriously. I am an audiobook narrator and I can't work because the drainage makes me hoarse. Any suggestions? I'm kind of at the end of my rope.
People coming here looking for medical advice--- you are misguided. Go to a doctor, I am not one.
I'm closing comments on this thread.