The dry scratchiness and painful swallowing that are the hallmarks of a sore throat can make you miserable. A sore throat — known medically as pharyngitis — is most often caused by a viral infection such as a cold or the flu (influenza).

What is it?

The dry scratchiness and painful swallowing that are the hallmarks of a sore throat can make you miserable. A sore throat — known medically as pharyngitis — is most often caused by a viral infection such as a cold or the flu (influenza). In many cases, a sore throat is the first sign that you're getting sick.

Sore throats are so common they're one of the main reasons people see a doctor. But many of those office visits aren't needed. In most cases, a sore throat is caused by a virus that soon goes away on its own. A sore throat is rarely caused by a bacterial infection that requires medical care or treatment with antibiotics. Until you're feeling better, over-the-counter medications and home treatments can help ease your symptoms.


Sore throat symptoms include:

  • A dry, scratchy or swollen throat
  • Pain when swallowing, breathing or talking

A sore throat usually occurs as a result of an infection that has its own additional symptoms. For example, if your sore throat is caused by a cold, you may also have coughing, fever, sneezing, body aches or a runny nose.

In most cases, the underlying cause of a sore throat — such as a cold or the flu — will get better on its own within a week. Less often, a sore throat is caused by something that needs treatment to get better.

Signs that your sore throat may have a more serious underlying cause — such as tonsillitis or strep throat — include:

  • White patches or pus on your throat or tonsils
  • Inability to swallow
  • A sore throat that doesn't get better on its own or keeps coming back
  • Vomiting
  • Skin rash
  • Headache
  • Severe throat pain
  • Swollen, red tonsils
  • A high fever — over 101 F (38.3 C) in babies under age 6 months or 103 F (39.4 C) in older children and adults


Most sore throats are caused by viruses — the same germs that cause colds and flu (influenza). Less often, sore throats are due to bacterial infections. Viruses and bacteria both enter your body through your mouth or nose — either because you breathe in particles that are released into the air when someone coughs or sneezes, or because you have contact with an infected person or use shared objects such as utensils, towels, toys, doorknobs or a telephone. Because the germs that cause sore throats are contagious, they can spread easily wherever large numbers of people congregate, such as schools, child care centers and offices.


The most common viral illnesses that cause a sore throat include:

  • Common cold
  • Flu (influenza)
  • Mononucleosis (mono)

Other viral illnesses that can cause a sore throat include:

Bacterial infections

Bacterial infections that can cause a sore throat include:

  • Strep throat
  • Tonsillitis
  • Diphtheria — a serious respiratory illness that's rare in industrialized nations but is more common in developing countries

Other causes

Other causes of sore throat include:

  • Allergies. The same pet dander, molds and pollens that trigger allergic reactions such as red, swollen eyes and a runny nose can also cause a sore throat.
  • Dryness. Dry indoor air, especially in winter when rooms tend to be overheated, can make your throat feel rough and scratchy, particularly in the morning when you first wake up. Breathing through your mouth — often because of chronic nasal congestion — also can cause a dry, sore throat.
  • Pollution and other irritants. Outdoor air pollution can cause ongoing throat irritation. But indoor pollution — especially tobacco smoke — is an even greater cause of chronic sore throat. Smokeless tobacco, alcohol and spicy foods can also inflame your throat.
  • Muscle strain. You can strain muscles in your throat just as you can strain them in your arms or legs. If you've ever gotten a sore throat after yelling at a concert or sporting event, you've likely strained your throat muscles. Your voice may also be hoarse (a symptom of laryngitis).
  • Acid gastroesophageal reflux disease (GORD). This occurs when stomach acid backs up into your food pipe (esophagus). Normally, a circular band of muscle (lower esophageal sphincter) blocks acid from coming up into the esophagus. But if the sphincter relaxes abnormally or weakens, stomach acid can back up, irritating your throat as well as your esophagus. Throat irritation caused by GERD doesn't occur with other symptoms of a viral illness, and it tends to be persistent, rather than lasting just a few days. It's also far more common in adults than in children. In many cases, you can prevent or reduce acid reflux with simple lifestyle changes — losing weight, avoiding foods that cause you discomfort and not eating right before bed, for example. When these aren't effective, over-the-counter or prescription medications may offer some relief.
  • HIV infection. HIV-positive people sometimes develop a chronic sore throat. This is due to a secondary infection such as oral thrush or cytomegalovirus, a common viral infection that can be extremely serious in people with compromised immune systems.
  • Tumours. If you smoke or abuse alcohol, you're at high risk of tumors of the throat, tongue and voice box. In some people these tumors cause few, if any, signs and symptoms. In others, they can lead to hoarseness, difficulty swallowing and sore throat. 

Risk factors

Although anyone can get a sore throat, some factors make you more susceptible to throat problems. These factors include:

  • Age. Children and teens are most likely to develop sore throats. Children are also more likely to have strep throat, the most common bacterial infection associated with a sore throat.
  • Smoking or exposure to secondhand smoke. Tobacco smoke, whether primary or secondary, contains hundreds of toxic chemicals that can irritate the throat lining.
  • Allergies. If you have seasonal allergies or ongoing allergic reactions to dust, molds or pet dander, you're more likely to develop a sore throat than are people who don't have allergies.
  • Exposure to chemical irritants. Particulate matter in the air from the burning of fossil fuels as well as common household chemicals can cause throat irritation.
  • Chronic or frequent sinus infections. Drainage from nose or sinus infections can cause throat infections as well.
  • Living or working in close quarters. Viral and bacterial infections spread easily anywhere people gather — child care centers, classrooms, offices, prisons and military installations.
  • Poor hygiene. Washing your hands carefully and often is the best way to prevent many viral and bacterial infections.
  • Lowered immunity. You're more susceptible to infections in general if your resistance is low. Common causes of lowered immunity include diseases such as HIV and diabetes, treatment with steroids or chemotherapy drugs — even stress, fatigue and poor diet.


Most conditions that cause sore throats aren't serious and go away on their own without causing any complications. However, some bacterial and viral infections can lead to other, more serious problems.

Strep throat, a bacterial infection, can trigger other conditions that include:

Common signs and symptoms of strep throat include:

  • Painful swallowing
  • Red and swollen tonsils, sometimes with white patches or streaks of pus
  • Tiny red spots on the soft or hard palate — the area at the back of the roof of the mouth
  • Swollen, tender lymph glands (nodes) in your neck
  • Fever
  • Headache
  • Rash
  • Stomachache and sometimes vomiting, especially in younger children

Mono (infectious mononucleosis) is a viral infection that can lead to complications including:

  • Inflammation of the spleen or ruptured spleen
  • Liver inflammation (hepatitis)
  • Low levels of blood cells involved in clotting (platelets)
  • Anaemia
  • Inflammation of the heart
  • Nerve damage, possibly leading to paralysis
  • Swollen tonsils, leading to obstructed breathing

Common signs and symptoms of mono include:

  • Fatigue
  • Weakness
  • Sore throat, perhaps strep throat that doesn't get better with antibiotics
  • Fever
  • Swollen lymph nodes in your neck and armpits
  • Swollen tonsils
  • Headache
  • Skin rash
  • Loss of appetite
  • Soft, swollen spleen
  • Night sweats


Most often, your doctor will diagnose the cause of a sore throat on the basis of a physical exam and a throat culture. During the exam, your doctor is likely to check your throat for redness and swelling and for white streaks or pus on your tonsils. Although these signs indicate an infection, there's no accurate way to tell by looking if the infection is viral or bacterial.

For that reason, your doctor is likely to take a throat culture or perform what's known as a rapid strep test to check for the presence of bacteria that cause strep throat. In either case, your doctor will rub a sterile swab over the back of your throat and tonsils to get a sample of the secretions.

In the past, the only way to accurately diagnose strep throat was to have these secretions cultured in a laboratory — a procedure that could take up to two days. Now, your doctor may use a rapid test that checks for bacterial infections within hours. Because rapid tests may miss a fair number of infections, your doctor may choose to have additional laboratory testing done as well.