Most cases of acute sinusitis start with
a common cold, which is caused by a virus. These viral colds do
not cause symptoms of sinusitis, but they do inflame the sinuses.
Both the cold and the sinus inflammation usually go away without
treatment in 2 weeks. The inflammation, however, might explain
why having a cold increases your likelihood of developing acute
sinusitis. For example, your nose reacts to an invasion by viruses
that cause infections such as the common cold or flu by producing
mucus and sending white blood cells to the lining of the nose,
which congest and swell the nasal passages.
When this swelling involves the adjacent
mucous membranes of your sinuses, air and mucus are trapped behind
the narrowed openings of the sinuses. When your sinus openings
become too narrow, mucus cannot drain properly. This increase
in mucus sets up prime conditions for bacteria to multiply.
Most healthy people harbor bacteria, such
as Streptococcus pneumoniae and Haemophilus influenzae, in their
upper respiratory tracts with no problems until the body's defenses
are weakened or drainage from the sinuses is blocked by a cold
or other viral infection. Thus, bacteria that may have been living
harmlessly in your nose or throat can multiply and invade your
sinuses, causing an acute sinus infection.
Sometimes, fungal infections can cause acute
sinusitis. Although fungi are abundant in the environment, they
usually are harmless to healthy people, indicating that the human
body has a natural resistance to them. Fungi, such as Aspergillus,
can cause serious illness in people whose immune systems are not
functioning properly. Some people with fungal sinusitis have an
allergic-type reaction to the fungi.
Chronic inflammation of the nasal passages
also can lead to sinusitis. If you have allergic rhinitis or hay
fever, you can develop episodes of acute sinusitis. Vasomotor
rhinitis, caused by humidity, cold air, alcohol, perfumes, and
other environmental conditions, also may be complicated by sinus
infections.
Acute sinusitis is much more common in some
people than in the general population. For example, sinusitis
occurs more often in people who have reduced immune function (such
as those with immune deficiency diseases) and with abnormality
of mucus secretion or mucus movement (such as those with cystic
fibrosis).
If you have asthma, an allergic disease,
you may have frequent episodes of chronic sinusitis.
If you are allergic to airborne allergens,
such as dust, mold, and pollen, which trigger allergic rhinitis,
you may develop chronic sinusitis. In addition, people who are
allergic to fungi can develop a condition called "allergic
fungal sinusitis."
If you are subject to getting chronic sinusitis,
damp weather, especially in northern temperate climates, or pollutants
in the air and in buildings also can affect you.
Like acute sinusitis, you might develop chronic
sinusitis if you have an immune deficiency disease or an abnormality
in the way mucus moves through and from your respiratory system.
In addition, if you have severe asthma, nasal polyps (small growths
in the nose), or a severe asthmatic response to aspirin and aspirin-like
medicines such as ibuprofen, you might have chronic sinusitis
often.
Because your nose can get stuffy when you
have a condition like the common cold, you may confuse simple
nasal congestion with sinusitis. A cold, however, usually lasts
about 7 to 14 days and disappears without treatment. Acute sinusitis
often lasts longer and typically causes more symptoms than just
a cold.
Your doctor can diagnose sinusitis by listening
to your symptoms, doing a physical examination, and taking X-rays,
and if necessary, an MRI or CT scan (magnetic resonance imaging
and computed tomography).
