Causes and Risk Factors of Sore Throat

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The pharynx, the cavity behind the nose and mouth that leads to stomach and lungs, is an easy target for infection and irritation that cause a sore throat. Disease-causing agents like respiratory viruses and bacteria prompt a sore throat—and are often, and in many cases, rightfully blamed when it strikes. But other causes must also be considered, including allergens, cigarette smoke, and even dry air. Certain health concerns, such as acid reflux, can also cause a sore throat. Even the simple act of shouting or singing loudly can injure the throat, causing pain and inflammation.

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Common Causes

While most people will know the cause of their sore throat, either because of an accompanying symptom or an identifiable injury, others may require a doctor to make the diagnosis. Here are the most typical causes of a sore throat, ranging from minor, localized infections to more serious, systemic disease:

Viral Infections

Viral infection accounts for more than half of all pharyngitis cases, and the common cold—caused by more than 200 types of virus, including adenoviruses, rhinoviruses, and coronaviruses—leads the way. 

A sore throat caused by a viral infection is often accompanied by nasal congestion, sneezing, runny nose, headache, and fever.

Tonsillitis can also develop.

Other viral infections associated with pharyngitis include:

  • Orthomyxovirus, a family of influenza viruses
  • Infectious mononucleosis, caused by the Epstein-Barr virus
  • Coxsackievirus and echovirus, causing blisters in the mouth and throat and herpangina pain in young children
  • Measles virus (proper vaccination can help prevent this)
  • Herpes simplex virus (HSV), which can cause an ulcerous lesion in the throat
  • HIV: a Sore throat and other flu-like symptoms can arise early in the infection. Later, sore throat may accompany secondary infections, such as cytomegalovirus and fungal infections.

While certain viral infections, like HSV, can be treated with antiviral drugs, many others (including measles, mononucleosis, and the common cold) have no cure.

Bacterial Infections

A number of bacterial infections can cause a sore throat. One of the most common is Streptococcus pyogenes, the bacteria associated with strep throat (streptococcal pharyngitis). It is thought to account for only 10 percent of sore throats in adults and young children but up to a third of sore throats in school-age children.

Strep throat is relatively minor but can sometimes lead to more severe infections. Strep does not cause respiratory symptoms like a cough and congestion.

Symptoms of strep throat can include fever, nausea, vomiting, a foul breath, and visible inflammation of the throat.

Less common bacterial throat infections include:

  • Neisseria gonorrhoeae (gonorrhea)
  • Bordetella pertussis (whooping cough)
  • Bacterial tonsillitis
  • Bacterial pneumonia

A rapid strep test can screen for strep throat. A throat culture can identify or help rule out a bacterial cause. Antibiotic treatment is based on which bacteria is found.

Fungal Infections

The most common cause of fungal throat infections is Candida albicans, a type of yeast that causes both oral thrush and yeast infection. Infection tends to occur in people with suppressed immune systems with the most severe cases often seen in people with advanced HIV infection. Others at risk include anyone who uses inhaled steroids, wears dentures or has uncontrolled diabetes.

Oral thrush (oral candidiasis) can often be symptom-free but, in some cases, can lead to soreness of the mouth, tongue, and throat. When it involves the esophagus, candidiasis is considered serious. Fungal infections like these are treated with antifungal medications.

Allergic Pharyngitis and Postnasal Drip

Allergic pharyngitis is inflammation of throat caused primarily by an allergen that enters the nose or mouth. You may experience this when your nose is stuffed up due to seasonal allergies, forcing you to breathe through your mouth. The tissues dry out, causing that scratchy feeling and irritation. You may also have postnasal drip as mucus drains from your nasal passages down the back of your throat. This can lead to inflammation of the throat and tonsils. Or, you may feel like you have a lump in the back of your throat.

Acid Reflux and GERD

Acid reflux occurs when stomach acid or bile backs up toward the throat. Both of these digestive fluids are irritating to the mucosal lining of the pharynx and esophagus. Acid reflux can cause a sore throat, particularly when you wake up in the morning or after you've been lying down for a while. Acid reflux occurs for many reasons including failure of the lower esophageal sphincter (LES) to close or a hiatal hernia.

While acid reflux may be the direct result of something you've had to eat or drink, it may also be a persistent condition referred to as gastroesophageal reflux disease (GERD). When stomach acid often gets up to the throat, this is called laryngopharyngeal reflux.

Other Concerns

Other possible causes of pharyngitis include:

  • Mouth breathing, especially when sleeping
  • Direct throat injury from ingesting hot liquids or chemicals, as well as trauma to the throat
  • Throat surgery or airway intubation during surgery for other sites, causing trauma and inflammation during healing
  • Muscle strain caused by talking loudly or for long periods of time
  • Benign vocal lesions caused by overuse or trauma to vocal cords
  • Epiglottitis (inflammation of the cover of the windpipe)
  • Peritonsillar abscess (a complication of tonsillitis)
  • Throat cancer
  • Antipsychotics and other drugs (such as pramipexole used to treat Parkinson's)


There is no known genetic component for the risk of most causes of a sore throat, although there may be a genetic predisposition to GERD.

There is also a genetic predisposition to developing a rheumatic fever after having strep throat.

It is thought that genetically susceptible children, especially if they live in poor social conditions, are more likely to get a rheumatic fever after a strep infection.

Lifestyle Risk Factors

Certain risk factors for a sore throat, like your body's reaction to an allergen, are out of your control. But here are some that you can have some influence over:

Irritants and Toxins

Exposure to certain substances can cause the direct inflammation of the pharynx and associated organs. Some are inhaled irritants like air pollution, cigarette smoke, and industrial fumes. Others are related to foods and other substances you ingest, such as alcohol, spicy foods, or chewing tobacco. 

Even dry air can be considered an irritant, as the lack of humidity can leave your throat feeling dry and scratchy.

This is common in arid climates. Both hot air and excessive air conditioner use can also cause throat irritation.


Infrequent hand washing makes it easier for you to contract illnesses related to germs you may pick up over the course of your day, including those that raise your risk of respiratory infection and related sore throat.

Flu Vaccination

Getting this annual shot can help reduce your risk of influenza.


Strep throat and colds can easily spread in places where large numbers of people interact, particularly in close quarters, such as military training facilities. According to the CDC, school children and those in daycare centers are prone to colds and the spread of strep throat due to being in groups with other children. Parents may also catch these infections from their kids. 

While you may not always be able to remove yourself from this kind of exposure, knowing this can help remind you to be diligent about practices that can help you avoid catching illnesses (especially during peak seasons), like hand washing and avoiding drinking fountains.

Use of Your Voice

You may also be prone to a sore throat if you tax your vocal cords and throat muscles by yelling, talking loudly, or singing for long periods.

Frequently Asked Questions

  • Am I more likely to get a sore throat during pregnancy?

    Yes. Changes in your immune system during pregnancy make you more susceptible to infections that cause a sore throat. You’re also more likely to suffer from heartburn and GERD, in which stomach acids irritate the throat.

  • What causes of a chronic sore throat?

    A chronic sore throat, defined as throat pain that lasts more than 12 weeks despite medication, can be caused by many conditions. The most common are tonsillitis, GERD, inflammation of the submandibular gland, and laryngopharyngeal reflux.

  • Can thyroid problems cause a sore throat?

    Yes. If your thyroid is enlarged, forming a goiter, it can cause a sore throat. Viral infections of the thyroid may also bring on pain. In rare instances, subacute thyroiditis, which is caused by a viral infection, can also cause throat pain and difficulty swallowing.

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