Unless you have prior experience with sinusitis, you may have trouble distinguishing it from other ailments, such as colds and allergies. People often mistakenly confuse the three because so many of their symptoms are similar.

But they are, in fact, different entities with different causes:

• Colds. Whereas sinusitis is caused by bacteria, colds are caused by viruses. These much smaller microorganisms invade the body’s cells, where they reproduce and are eventually released into the bloodstream to invade other cells.

The body’s immune system is usually quite effective at controlling viral infections, so most colds go away within a week. Colds can occur at any time but are most common during winter (the cold season). What can be confusing is that it’s not uncommon for a cold to precede a sinus infection.

• Allergies. Many of us have heard the old saying “If you sneeze more than three times, it’s an allergy.” Although not always correct, this does have some merit.

Allergies are usually caused by environmental irritants, such as pollen, dust mites, or pet dander, not bacteria or viruses. These irritants, known as allergens, activate an immune response that is different from the immune response to an infection.

An antibody called immunoglobulin E (or IgE for short) triggers a specific type of white blood cell called a mast cell to release granules of histamine into the bloodstream.

Histamine is a powerful molecule that causes the membranes of the upper respiratory tract, including the nose and sinuses, to swell and weep mucus. Histamine release can also trigger repeated sneezing and make your nose and eyes itch.

Allergies can be either perennial, meaning they occur year-round, or seasonal. Allergies to dust and pet dander are often perennial. Seasonal allergies tend to be worst during the spring, when flowers and trees bloom, and the fall, when ragweed is in the air. As with colds, allergies may precede and trigger sinusitis.

Table below lists many of the differences between sinusitis, colds, and allergies. Understanding these differences is helpful, but it won’t make your symptoms go away. If severe nasal symptoms linger for more than a week, it’s advisable to see your doctor.

Symptom	Sinusitis	Cold	Allergy
Facial pressure/pain	Yes	Sometimes	Sometimes
Duration of illness	More than 10 days	Less than 10 days	Varies
Nasal discharge	Thick, yellow-green	Thick and whitish thin or and watery	Clear, thin, watery
Itchy eyes	No	No	Yes
Headache	Yes	Sometimes	Sometimes
Bad breath	Sometimes	No	No
Cough	Sometimes	Yes	Sometimes
Nasal congestion	Yes	Yes	Sometimes
Sneezing	No	Yes	Yes
Fatigue/weakness	Sometimes	Yes	Sometimes
Sore throat	Sometimes	Yes	Sometimes

Primary Care Visit

Your primary care physician will begin by asking you to describe your current symptoms and how long you’ve had them. In addition to the Big Three—pain and pressure, difficulty breathing and congestion, and postnasal drip—she will probably inquire about other symptoms, such as loss of smell, sore throat, cough, and fatigue.

She will also ask about your history: Have similar symptoms occurred in the past? How often? What medications have you tried? Do you have allergies? Do you smoke? What are your home and work environments like? Try to be prepared to answer these questions as thoroughly as possible.

A good patient history is the single most important tool your doctor has to confirm the diagnosis of sinusitis. This same history is also critical for determining whether something other than sinusitis could be causing your problems.

For example, if you only have facial pain without congestion or drainage, your problem could be neurological in nature, with migraine headaches and neuralgia as possibilities, and you may be referred to a neurologist.

And if you are sneezing and have itchy eyes and your postnasal drip remains thin and watery, it’s likely you have allergies, and you may be referred to an allergist.

Once the history is completed, your primary care physician may look inside your nose with a small flashlight. She won’t be able to see into your sinuses, but she can see the front portion of the inferior turbinates and assess how much swelling there is and whether any pus is present.

Some doctors may also tap on your forehead or cheeks—a technique known as percussion of the sinuses—and ask you if it hurts. Although there’s no harm from tapping, you should be aware that it’s not a reliable indicator of sinusitis.

Many patients who have sinusitis have no sinus tenderness during an infection, while others with completely normal sinuses will complain of pain when their forehead or cheeks are tapped.

CT Scan

While a careful patient history with a nasal examination is often enough to determine whether you have sinusitis, your doctor may also order a computed tomography (CT) scan to confirm the diagnosis. A CT scan is a radiological technique that has largely replaced plain sinus x-rays for evaluating sinus disease.

A CT scan is a series of x-ray pictures, each a thin slice ranging from one to three millimeters in thickness, that combine to form a threedimensional view. It allows your doctor to view the interior of your nose and sinuses in exquisite detail. A CT scan of the sinuses is painless and takes less than five minutes.

You lie down on a table that slides through a large doughnut-shaped scanner. With newer models, you can see above and below this device, so claustrophobia is not a problem. There are two kinds of sinus CT scans: limited and full.

A limited scan typically shows four or five vertical slices, with at least one cut through each of the sinuses to identify any polyps, cysts, or entrapped fluid. A full scan usually involves more than twenty vertical and horizontal slices.

The larger number of slices enables your doctor to see the individual sinus ostia, including the OMC, and whether or not they’re blocked. A limited scan is less expensive than a full scan; in general, primary care doctors order limited scans, and ear, nose, and throat (ENT) specialists order full scans.

Either way, results are usually available within minutes and may be viewed on printed films or a computer screen. On a CT scan, air shows up black and bone appears white, as shown in Figure below.

This sinus CT scan shows normal air-filled sinuses, which are black in appearance, on the left side. On the right side, obstructed maxillary and ethmoid sinuses are shown; they appear gray because they are filled with fluid.

Gray areas in the sinuses often signify abnormalities, such as pus, mucus, polyps, or cysts. When looking at sinus CT scans, you should keep in mind the general rule of thumb that black is good and gray is bad, with cysts being one exception.

Treatment and Referral

If your doctor concludes that you have sinusitis, in most cases she will prescribe an antibiotic and advise you to take an over-thecounter decongestant. If she believes allergies are playing a role, she may also prescribe a nasal steroid spray and recommend an antihistamine. I’ll discuss these and other medications in detail later.

A course of antibiotics will often eliminate the infection or at least reduce it to the point that your symptoms recede. But if the sinus blockage remains, the infection may return a short time later. If you have more than three sinus infections in a year, your primary care doctor may refer you to an ENT specialist, also known as an otolaryngologist.

It’s not difficult to find a qualified ENT specialist. Most primary care doctors have a group of ENT specialists they regularly refer patients to. As a general rule, if you’re comfortable with your primary care physician, you should have confidence she will refer you to a capable ENT specialist.

You might also ask your friends for recommendations. The point to be made here is that any ENT specialist certified by the American Board of Otolaryngology (see aboto.org) has the training and expertise to treat sinusitis.

Off to the ENT Doctor

Like a primary care physician, an ENT doctor will begin by asking you about your history of sinusitis. This history may go into greater detail, especially if it’s your first encounter with this doctor. Next, he will likely examine your nose, using a nasal speculum to gently spread your nostrils and look inside.

If he wishes to get a closer view, he’ll use an endoscope, a thin, high-resolution telescope with a light on one end and an eyepiece on the other. Figure below shows an endoscopic examination.

Nasal endoscopy is mildly invasive, so he’ll first spray your nasal passages with a topical decongestant (which enlarges the nasal passages by temporarily reducing swelling in your mucous membranes) and a mild topical anesthetic (which reduces the tickle sensation and prevents you from sneezing).

These medications help ensure that endoscopy is not painful, although some people may still find it mildly uncomfortable. Endoscopy gives your ENT doctor a detailed view of what’s going on in your nasal cavity. He can see four important things:

• if the mucous membranes are inflamed
• if the middle meatus is draining pus
• if the turbinates are enlarged
• if polyps are blocking the sinuses

Polyps are small growths ranging in size from a pea to a grape that are attached by tiny stalks to the sinus walls, as shown in Figure below. Although the precise cause of polyps is unknown, they tend to occur in individuals whose sinus mucosa is chronically inflamed.

As polyps continue to grow, they eventually block the nasal airway, causing congestion, difficulty breathing through the nose, and an impaired sense of smell. When polyps become large enough, they block the sinus drainage passages, leading to overgrowth of bacteria and the resultant pain of a sinus infection.

In addition to polyps, another common finding during endoscopic examination is enlarged turbinates. The inferior turbinates, in particular, can become large and swollen from what’s known as allergic rhinitis (literally, “inflamed nose”).

Unlike sinusitis, this form of environmental allergy causes swelling of the nasal passages but leaves the sinuses unaffected. People with allergic rhinitis have many of the same allergy symptoms as those listed in Table above, but their CT scan shows clear sinuses. Allergy medications will usually provide relief.

If not, your doctor may want to refer you for allergy testing. Endoscopy does not enable an ENT specialist to view inside your sinuses because the ostia are too small for the endoscope to enter. To learn what’s going on inside the sinuses, your ENT doctor will probably obtain a sinus CT scan, if you haven’t already had one.

Other Tests

In almost all cases, a detailed patient history, nasal endoscopy, and a CT scan will provide your ENT doctor with all the information he needs to make an accurate diagnosis. Occasionally, though, additional tests are ordered. An MRI is usually not one of them.

• Allergy tests. If environmental allergies appear to be the underlying cause of your sinusitis, you may be a candidate for allergy testing. Skin tests entail exposing your skin to a large variety of allergens (substances that trigger allergies) by either pinprick or needle injection.

An alternative to skin testing is a radioallergosorbent test (RAST), a blood test that measures amounts of an antibody (IgE) your body produces to fight allergies. Both skin tests and RASTs are commonly performed by allergists and otolaryngologists with expertise in allergies.

• Cultures. If endoscopy shows pus, an ENT specialist may obtain a culture with a small Q-tip to determine which bacteria are present and how sensitive they are to various antibiotics. These endoscopically guided cultures may be particularly helpful for patients who have not responded as expected to antibiotics.

A second type of culture—those performed by placing a large Q-tip in the nostril (also called a nasal swab)—can be problematic because it’s hard to distinguish between bacteria that are harmful and cause sinus infections and bacteria that harmlessly live in the nose.

• Blood tests. Your physician may order general blood tests if he suspects you have a systemic (whole-body) illness that’s triggering your sinusitis.

Depending on the duration of your symptoms, you may be diagnosed with either acute or chronic sinusitis. The causes and treatment options for these two types can be very different. Next, we’ll take a look at acute sinusitis.