why would the glands behind your ear swell
In addition, it is also possible for swollen or enlarged salivary glands to also form a lump in the area you are describing behind the ear. This can sometimes occur if part of the duct draining the salivary gland into the mouth becomes clogged.
There are many small glands behind the ear, and in neck region. They act as protective glands. If there is any type of infection the lymph glands are first to react and in doing so they become swollen. They stop the infection from spreading. Your child may be having infection on scalp or around the ears.