Kim Richard Jones, M.D., Ph.D.
Adult and Pediatric Otolaryngology
Kathy Yu, M.D., M.P.H.
Adult and Pediatric Otolaryngology
Carolina ENT Associates 55 Vilcom Center Drive, Suite 140
Chapel Hill, NC 27514
phone: 919.942.7278
fax: 919.942.9029
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Sinusitis & Colds

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A cold is an upper respiratory infection that is caused by any number of viruses. It generally goes away on its own in 7-14 days, and antibiotics are not indicated, since they act against bacteria and not viruses. The symptoms of a cold, such as nasal congestion, runny nose, etc. are primarily from the effects of the viruses on the lining of the nose, which is called mucosa. However, one of the problems with trying to tell the difference between a cold and a sinus infection is that the lining of the sinuses is similar to the lining of the nose. Thus, a cold virus will often infect the mucosa of the sinuses as well as that of the nose. In fact, it has been proposed that the standard medical term for a cold (“rhinitis”, meaning “inflammation of the nose”) would be more accurate if it were changed to “rhinosinusitis”.

In contrast to a viral cold, when people use the term “sinus infection”, they usually mean a bacterial infection confined primarily to the sinuses. A bacterial infection differs from a viral infection in that it generally produces more inflammation, and often draws millions of the body’s white blood cells to help combat the infection. The white, thick discharge that is typical of a bacterial infection (but rarely seen with a viral infection) is in fact composed of dead bacteria and white cells. The body’s immune system will usually control a bacterial infection, but it may take longer than controlling a viral infection and is sometimes not entirely successful. For example, studies have shown that about two-thirds of bacterial sinus infections will eventually resolve on their own, but 1/3 will require antibiotics to become completely eradicated.

Why is it important that we should try to distinguish between a viral cold and a bacterial sinus infection? The most important reason is the overuse of antibiotics. While antibiotics may or may not be used for bacterial infections, they should never be used for viral infections. Thus, every time a patient gets an antibiotic for a viral cold, it increases the risk of that patient developing an antibiotic-resistant infection in the future. Also, it’s expensive…a ten-day course of many antibiotics can run over $100.00.

So, since both viral and bacterial infections can occur in the sinuses, how does one tell them apart? Since both share many similar symptoms (see below), there is always a bit of guesswork involved, and sometimes sinus x-rays or even a CT scan of the sinuses may be helpful. The first step is an educated patient, who goes to the doctor when appropriate and understands that antibiotics may not be necessary, at least not initially. The following information is thus presented to allow you, the patient, to make a more informed decision as to when to become concerned that you may have a sinus infection. Further information may be found on this website in the sections Sinusitis and Sinus Headaches.

Symptoms That Can Be Seen
With Either a Sinus Infection or a Cold

1) Nasal Congestion

Since both cause swelling of the nasal mucosa, nasal congestion can be seen with either a cold or a sinus infection.

2) Colored Nasal Discharge

It is definitely not true that colored nasal discharge means you have a sinus infection. Towards the end of many viral colds, the nasal discharge changes from clear to colored (usually green) because of a change in the thickness of the mucous the nose makes. True pus, such as is seen with pure bacterial infections, is usually white or yellowish-white and is thick like cream.

3) Postnasal Drip

Postnasal drip is usually not the result of too much mucous being made, but rather mucous getting too thick. The normal nose makes up to one quart (!) of mucous a day, and ordinarily it is just pushed to the back of the nose and swallowed. When we become aware of it, it’s because it has gotten too thick to be easily swallowed, and “hangs up” in the back of the throat. Since both viral and bacterial infections can make nasal mucous more thick, both can thus cause a sensation of postnasal drip.

4) Fever

Fever is caused by our body fighting off an infection, and can also be seen with either viral or bacterial infections. A fever of less than 100 degrees is usually not significant, even if your usual body temperature runs less than 98.6 degrees.

5) Facial Pressure and Pain

Although we don’t know what actually causes these symptoms, the most likely cause is probably swelling of the mucosa in the sinuses. Since by now you should know that both viral and bacterial infections can cause this type of swelling, it should come as no surprise to also know that these symptoms can be seen with either a viral or bacterial infection.

How to tell the Difference
Between a Sinus Infection and a Cold

1) Time

The length of time you’ve been sick is probably the most reliable way to tell if you have a viral cold or a bacterial sinus infection. Most colds are gone or at least starting to improve by ten days. If your symptoms haven’t started to improve by day 10, or if you’re getting worse after 7 days, it’s more likely that you have a bacterial infection. Also, the most common way that a bacterial infection starts is following a viral cold, since the cold virus weakens the sinuses ability to defend themselves against bacteria. Thus, if you have a cold, start to get better, and then get even sicker, you may have what is called a “secondary” bacterial infection.

2) Symptoms On Only One Side

Most cold viruses affect all of the nasal and sinus mucosa equally, which is why you don’t get a cold on just one side of your nose. Bacterial infections, on the other hand, can involve one to several sinuses, sometimes just on one side and sometimes on both sides. Thus, if your symptoms such as nasal congestion, pressure, etc. are exclusively on one side, it is more likely you have a bacterial infection.

3) Tooth Pain

Pain in the upper teeth is suggestive of a bacterial infection.

Other Tests That May Be Considered

1) Nasal Endoscopy

This is a procedure in which a small telescope is used to examine the inside of the nose. It cannot be used to look into the sinuses themselves (unless you have had previous surgery to open the sinuses), since the natural openings are so small. However, it can determine whether any pus is coming out of the opening (indicating bacterial sinusitis) or, conversely, if the opening looks normal. Since these scopes are quite expensive, they are usually only used by ENT specialists.

2) Sinus X-rays or CT Scans

These studies are more useful in determining whether chronic symptoms (those lasting months rather than days or weeks) are due to sinus problems, but are sometimes used to differentiate between a cold or bacterial sinusitis. Looking at the images of the sinuses that either produces, sinus mucosal thickening can be seen with either a viral or bacterial infection, but an air-fluid level or opacification of a sinus (the whole sinus is filled with pus or fluid), is suggestive of a bacterial infection.

3) Bacterial Cultures

These are not helpful, as billions of bacteria are present in the healthy nose, and if you stick a culture swab in the nose, some bacteria will always grow in the culture. In fact, some unscrupulous ENT physicians use these culture results to convince patients that they have a “chronic sinus infection” and then recommend unnecessary sinus surgery.


Distinguishing a sinus infection from a cold is difficult even in the best of circumstances. This is largely because many of the symptoms popularly associated with the diagnosis of “sinusitis” can in fact be seen with viral infections as well. In general, a visit to the doctor is not indicated until you have been sick for at least seven days, since until then, there is little to distinguish between a cold and a sinus infection.
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