Merck Manual

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Throat Infection

(Pharyngitis; Tonsillitis; Tonsillopharyngitis)


Clarence T. Sasaki

, MD, Yale University School of Medicine

Last full review/revision Jan 2020| Content last modified Jan 2020
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Infections of the throat and/or tonsils are common, particularly among children.

  • Throat infections are usually caused by a virus but may be caused by bacteria such as streptococcal bacteria.

  • Symptoms include severe pain with swallowing and swollen, red tonsils.

  • The diagnosis is based on an examination of the throat.

  • If untreated, tonsillopharyngitis that is caused by bacteria may become a tonsillar abscess.

  • Pain is relieved with analgesics, and a streptococcal infection is treated with antibiotics.

  • Sometimes the tonsils have to be surgically removed.

The tonsils contain lymphoid tissue that is part of the body's immune defense system. Thus, the tonsils and nearby throat tissue frequently become infected by organisms that enter the nose and throat.

People who have had their tonsils removed can still get throat infections.


Throat infections are usually caused by a virus. Most often, it is one of the viruses that cause the common cold, such as rhinovirus, adenovirus, influenza virus, or respiratory syncytial virus. Less often, another virus is involved, such as the Epstein-Barr virus (which causes mononucleosis) or human immunodeficiency virus (HIV).

In less than one third of people, throat infections are caused by a bacterial infection. Group A streptococcus (strep throat) is the most common bacterial cause and usually occurs in children between age 5 and age 15. Strep throat is less common in children under age 3 and in older adults. Untreated strep throat sometimes causes complications. Complications can include tonsillar cellulitis or abscess, rheumatic fever, and kidney inflammation (glomerulonephritis). Rarely, bacterial infections such as gonorrhea and diphtheria cause throat infections.


People with a throat infection have severe pain with swallowing and usually speaking. The pain is sometimes also felt in the ears. Some people have fever, headache, and an upset stomach. The tonsils are red and swollen and sometimes have white patches on them. Lymph nodes in the neck may become swollen and tender.

In people who have frequent tonsil infections, the normal small pits in the tonsils sometimes become filled with white, hardened secretions that resemble tiny stones. These stones can trap odor-causing bacteria, causing chronic bad breath, and can predispose people to subsequent bouts of tonsillitis.

People with a cold virus infection often have a runny, congested nose and a cough. People with mononucleosis often feel extremely tired and have many swollen lymph nodes, and their increasing tonsillar swelling may begin to block air when a person breathes, causing noisy breathing.


  • A doctor's evaluation

  • Sometimes tests to check for strep throat

Doctors recognize a throat infection by viewing the throat. However, because viral infections and bacterial infections often cause the same appearance in the throat, it is difficult for doctors to know whether the cause is a viral or bacterial infection just by looking at the throat. However, people with a runny nose and cough are more likely to have a viral infection.

Because it is often considered important to identify strep throat (which is generally treated with antibiotics), doctors sometimes swab the person's throat and do tests to identify streptococcus bacteria. Typically, doctors test most children but test adults only if they meet certain criteria, such as having white patches on the tonsils (tonsillar exudates), swollen and tender lymph nodes in the neck, fever, and an absence of cough. However, not all experts agree on when testing should be done or even when antibiotics should be given.


  • Pain relievers (analgesics)

  • For strep throat, antibiotics

  • Sometimes surgical removal of the tonsils

Analgesics given by mouth, such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs), often help reduce pain in people with a throat infection. Gargling with warm salt water has often been recommended but has not been shown to help. Some doctors also give a single dose of a corticosteroid, dexamethasone, which may shorten the duration of symptoms. It may also help lessen airway blockage caused by mononucleosis.

People with a strep infection are given an antibiotic, usually penicillin or amoxicillin. People who are allergic to penicillin may be given clindamycin.


People who have repeated streptococcal infections of their tonsils may need to have their tonsils removed (tonsillectomy), according to suggested guidelines.

Typically, it is children who need tonsillectomy, including children who have had more than 7 infections in 1 year, more than 5 infections in each of 2 years, or more than 3 infections per year for 3 years. Doctors consider tonsillectomy if the child has an acute infection that is severe and persistent despite being treated with antibiotics, if the child has significant obstruction (including obstructive sleep disorder) or a recurrent peritonsillar abscess, or if they suspect cancer.

For adults, doctors do not use these specific criteria for when to do tonsillectomy. However, doctors may do tonsillectomy in adults who have severe bad breath due to tonsillar stones.

For both children and adults, doctors do allow for individual differences when deciding whether to recommend a tonsillectomy.

There are numerous effective techniques for tonsillectomy. Doctors can use a scalpel or an electrocautery device, or they can destroy the tonsils using radio waves.

Fewer than 2% of people, adults more than children, have bleeding complications resulting from a tonsillectomy. Bleeding typically occurs within 24 hours of surgery or after about 7 days. People who have bleeding after a tonsillectomy should go to a hospital.

Partial tonsillectomy is sometimes done in patients with tonsillitis that causes some blockage in the throat. Part of the enlarged tonsil can be removed by shaving the tonsil using special scissors, or using other devices such as laser, radiofrequency, or electrocautery. It works as well as total tonsillectomy to relieve airway obstruction that is causing snoring and interruption of sleep. Tonsils do not usually grow back, and what is left after partial tonsillectomy is helpful in maintaining immune function during early childhood.

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