What causes lymph nodes to swell?

Sink traps: Lymph nodes are sink traps for our bodies. If you have infection or inflammation somewhere, your friendly hardworking lymph nodes will catch bits, work on it, & swell. They may feel tender. They may not hurt at all. Example: common cold & swollen neck lymph nodes. See your doc if you're concerned, if there's not an obvious neighborhood reason why your nodes are swollen, if it's more than 3-4 weeks.

Several things: Cancer, infection or autoimmune diseases.

Swollen nodes.: Nodes can swell because of infection or inflammation (some people refer to lymph nodes and tonsils as "glands") or because of local obstruction of their drainage (as in the salivary glands). So the best answer would depend on to which glands or nodes you are referring.