What causes the occipital gland to swell on one side. how long does it take for swelling to go away.

Lymphadenopathy: Lymph nodes enlarge in response to some inflammatory process that they are trying to contain. In the occipital area it may be an inflamed hair root, middle ear infection with involvement of the mastoid sinuses, and so on. If this node is not stony hard, fixed to underlying tissue, and increases in size it may need to be biopsied sometime in the future. See your pcp.