An infection caused by germs called bacteria that affect the mastoid bone behind the ear.

Mastoiditis is a serious infection that is more common in children. Getting lots of ear infections raises the risk of mastoiditis. So does getting a serious ear infection. Without treatment, these infections can spread from the middle ear to the mastoid bone.

Mastoiditis symptoms can include pain, soreness or tenderness behind the ear. The skin behind the ear may change color. The ear may stick out, and fluid called discharge may leak from it. Fever, tiredness and headache also can happen. Without treatment, mastoiditis can cause complications such as hearing loss.

Mastoiditis treatment involves taking medicines called antibiotics that help get rid of the germs. If the antibiotics don't help enough, a procedure that uses a needle to drain pus from the ear may be done. Or surgery to remove part of the mastoid bone may be needed.