Sinusitis Causes
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What are some causes of acute sinusitis?
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 or HIV infection) and with abnormality of mucus secretion or
mucus movement (such as those with cystic fibrosis).

What causes chronic sinusitis?
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 (e.g., immune deficiency, HIV
infection, and cystic fibrosis). 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.

Other possible causes include eating too many dairy products or fatty
foods or not eating enough green vegetables. A lack of exercise and
deep breathing or poor circulation may also contribute to sinus
problems.
What is Sinusitis?
Sinusitis Symptoms
Sinusitis Treatment
Prevention
Research

References and Sources: Medline, Pubmed, National Institutes of Health

last update: December 2008