How a Sinus Infection Is Diagnosed

The diagnosis of a sinus infection (sinusitis) is usually based on symptoms and a physical exam. If your symptoms don't improve with treatment, you may need X-rays or a CT scan. Sometimes a sample of sinus fluid may be taken for microscopic exam and culture (growing the sample in a lab to identify the infectious organism).

Though not all sinus infections require treatment, early diagnosis and treatment (if necessary) can help you feel better sooner and potentially prevent the infection from progressing.

sinusitis diagnosis
© Verywell, 2018 

Self-Checks

Most sinus infections are caused by a viral infection, such as the viruses that cause the common cold.

A cold should get better in about a week—that goes for infants, children, and adults. The virus can involve the sinuses and produce nasal congestion, sinus pressure, and clear mucus drainage for as long as 10 days. At that point, a viral sinus infection should begin to improve on its own.

Pay attention to details about your sinus infection—such as when your symptoms began and how they have progressed. This information will be helpful to your healthcare provider if your symptoms persist.


However, if your symptoms are not getting better after 10 days—or if they've improved, but then worsened—a bacterial sinus infection may have developed.

Other signs of a bacterial infection include:

  • A persistent or high fever
  • Severe sinus pain, especially on only one side
  • Discolored nasal discharge, especially on just one side

If you have these symptoms, you should call your healthcare provider to get an appointment for an examination and diagnosis.

If you experience severe symptoms, including changes in your vision, swelling around the eyes or forehead, severe headache, or confusion, you should see your healthcare provider immediately.

These are serious signs that a bacterial sinus infection is spreading.

Examination

Sinus infections can be diagnosed and treated by your child's pediatrician or your primary care provider.

If you've had four or more sinus infections in a year, your healthcare provider will consider whether you have contributing factors that are increasing your risk. Known risk factors include a history of allergies, asthma, environmental changes, and any conditions that could weaken your immune system.

During your physical exam, your healthcare provider will check inside your nose with a speculum and flashlight. They will note any areas of pain or tenderness and look for purulent (pus-filled) drainage in your nose and throat. Your nose examination will also identify whether you have a foreign body, deviated septum, nasal polyps, tumor, or nosebleed.

Labs and Tests

Your healthcare provider may run some tests, but this is not routinely done.

Your tests may include:

  • A culture of nasal drainage collected via a swab of the nose or sinus
  • Blood tests (erythrocyte sedimentation rate, CBC, C-reactive protein)
  • Allergy testing, especially for a chronic sinus infection or repeat sinus infections

Imaging and Procedures

Imaging usually isn't done in cases of acute sinusitis. But you may need imaging for an evaluation of chronic sinusitis or recurrent sinusitis to look for structural causes. You may also need imaging if you have severe acute symptoms or signs that your infection might be spreading. 

An X-ray sinus series can usually identify fluid in the sinuses or nasal polyps. A computerized tomography (CT) scan gives a more thorough view of the sinuses, and it is usually preferred. Magnetic resonance imaging (MRIs) are less commonly used because they don't distinguish air from the bone.

Diagnostic Procedures

You may have a procedure to examine the structures of your nose and nasal passages or to obtain a sample of fluid to be sent for culture. You may be referred to an ear nose and throat (ENT) specialist for these procedures. Most cultures are done with endoscopy.

A rhinoscopy is a nasal endoscopy that allows your provider to look into the nasal passages. The nasal endoscope is a thin tube that is inserted into your nose to see your nasal passages and sinuses. It contains a light, fiberoptic cable, and a lens for viewing. It may be attached to a video camera so the healthcare provider can see the images on a screen and record the exam.

To make you more comfortable during rhinoscopy, you'll be given a nasal decongestant spray and a local anesthetic spray to numb the nose. This exam can be used to check for nasal polyps, a deviated septum, enlarged turbinates, tumors, and pus. It can be used to remove a sample of tissue so your healthcare provider can check for bacterial or fungal infection.

A sample can also be obtained with a sinus puncture in order to avoid contamination with bacteria found in the nasal passages. Sinus puncture is done by numbing the puncture site (usually just below the nose or inside the mouth), inserting a needle, and withdrawing an aspirate.

Differential Diagnoses

Your healthcare provider may consider several causes of your symptoms, including allergies, viral, bacterial, or fungal infection. 

Allergic rhinitis typically has clear nasal drainage rather than the thick, yellow or green drainage seen in bacterial or fungal sinusitis.

  • Your healthcare provider may refer you for allergy testing if this is a concern.
  • If you primarily have facial pain and a headache, the cause could be a migraine 
  • Sometimes a foreign body may get stuck up the nose and cause inflammation. This is more common among children.

It can be harmful for you to take antibiotics unnecessarily, so your healthcare provider will usually wait to see if your symptoms get better over the course of a few days before prescribing antibiotics. The waiting period before treating with antibiotics helps your healthcare provider ensure they aren't overprescribing antibiotics, which will not help resolve viral sinusitis, allergic rhinitis, or other non-infectious inflammatory reactions, and can lead to bacterial resistance.

If your symptoms persist for more than 10 days or if you have a fever, your healthcare provider may prescribe antibiotics on the presumption that you have acute bacterial sinusitis.

Acute sinusitis will usually clear up by four weeks.

Once you have had the symptoms for 12 weeks it will be called chronic sinusitis.

Causes of chronic sinusitis include allergies, allergic fungal sinusitis, fungal sinusitis, nasal polyps, benign or malignant sinonasal tumors, enlarged turbinates, or a deviated septum.

Frequently Asked Questions

  • How is a fungal sinus infection diagnosed?

    In addition to a physical exam, your healthcare provider may order a nasal endoscopy and a CT scan. They may also take samples of mucus and tissue to send to the lab in order to identify what's causing the infection.

  • When should you have an antibiotic for a sinus infection?

    Antibiotics are only effective for sinus infections caused by bacteria. Your healthcare provider will consider your symptoms and how long you've had them to determine whether you have a bacterial sinus infection. Some signs of bacterial sinusitis include symptoms for at least 10 days or symptoms that seemed to be improving but got worse again.

Was this page helpful?
5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Common Cold Symptoms, Treatment & More. Cleveland Clinic. Oct 7, 2014.

  2. Rosenfeld RM, Piccirillo JF, Chandrasekhar SS, et al. Clinical practice guideline (update): adult sinusitis. Otolaryngol Head Neck Surg. 2015;152(2 Suppl):S1-S39. doi:10.1177/0194599815572097

  3. Al-hashel JY, Ahmed SF, Alroughani R, Goadsby PJ. Migraine misdiagnosis as a sinusitis, a delay that can last for many years. J Headache Pain. 2013;14:97. doi:10.1186/1129-2377-14-97

  4. Radojicic C. Sinusitis. Cleveland Clinic Center for Continuing Education.. Aug 2012.

  5. University of Washington Medical Center. Department of Otolaryngology–Head and Neck Surgery. Fungal sinusitis.

Additional Reading