What Causes Swollen Tonsils?

Woman having pain with a sore throat.
Swollen Tonsils. Stockbyte/Getty Images

To understand what causes swollen tonsils you must first understand what tonsils are. It is believed that the tonsils are part of the lymphatic system and help to protect against viruses and bacteria. After being trapped by the tonsils, inhaled particles are then transported to the lymphatic system and disposed of by the immune system. However, occasionally there is a glitch in the system. Sometimes, the tonsils become infected by the bacteria and viruses.

This causes swelling, redness, pain, and in some cases white or red spots on the tonsils. Common infections that cause swollen tonsils include:

Because complications of strep throat can be serious, you should see a doctor to have a strep test if you have swollen tonsils, especially if they are accompanied by redness and throat pain. It is also interesting to note that a condition called cryptic tonsils can make it appear as though there are white spots of pus on the tonsils even though the tonsils are not really infected. Occasionally strep infections can become chronic and difficult to cure. Chronic strep infections sometimes make surgical removal of the tonsils necessary.

Swollen tonsils caused by bacterial infections can be treated with antibiotics.

Symptoms usually go away within a few 24 hours after starting medication. There is no medication that can kill a viral infection but it may be possible to reduce your swollen tonsils using steroid medications. However, since steroid medications have many side effects most doctors are hesitant to prescribe these medications unless the tonsils are extremely swollen and bothersome.

Non-infectious causes of swollen tonsils are rarer but may include:

  • cancer of the tonsils (rare)
  • cryptic tonsils (tonsil stones)

In some cases, tonsils may become so swollen that it may interfere with breathing or swallowing or cause obstructive sleep apnea. Sleep apnea is a serious condition that causes a person to stop breathing for a brief period of time while sleeping. Studies have shown that sleep apnea can lead to daytime fatigue, depression, mood swings and more serious health conditions including high blood pressure and heart disease. Obstructive sleep apnea is also a leading indication for tonsillectomies in the United States.


American Academy of Otolaryngology - Head and Neck Surgery. Fact Sheet: Tonsillitis. Accessed: January 22, 2011 from http://www.entnet.org/HealthInformation/tonsillitis.cfm

Medscape. Tonsillitis and Peritonsillar Abscess. Accessed: April 30, 2016 from http://emedicine.medscape.com/article/871977-overview#a6

Medline Plus. Tonsillitis. Accessed: January 22, 2011 from http://www.nlm.nih.gov/medlineplus/ency/article/001043.htm

National Sleep Foundation. Sleep Apnea. Accessed: April 30, 2016 from https://sleepfoundation.org/sleep-disorders-problems/sleep-apnea

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