Tonsillitis is an inflammation of the tonsils, the fleshy clusters of tissue on both sides of the back of the throat. Tonsils normally filter germs that enter the body through the mouth.

More to Know

Tonsillitis is typically caused by either a virus like the common cold virus or the Epstein-Barr virus (which also causes mono), or by group A Streptococcus bacteria (also the cause of strep throat).

Most types of tonsillitis are contagious, spreading from person to person by contact with the throat or nasal fluids of someone who is infected. Tonsillitis symptoms include a sore throat, fever, swollen glands in the neck, and trouble swallowing.

Keep in Mind

If tonsillitis symptoms appear, call your doctor. Treatment depends on whether tonsillitis is caused by a virus or by bacteria. If due to a virus, the body will fight off the infection on its own. If it's caused by strep bacteria, the doctor probably will prescribe an antibiotic.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.