How long is it supposed to it take for a lymph node to swell?

Monitoring Centers. The lymphatic system absorbs and carries things too big to go into the arteries and veins like bacteria eaten by white cells and digested food. A lymph node "tastes" the lymph to see if anything bad is there like bacteria, viruses, cancers, etc. When it detects a problem, it alerts the immune system and swells in response to the inflammation they create when they react. Can occur quickly.