What are the causes of your groin lymph nodes to become swollen?

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 enlarges in response to the inflammation they create when they react. You can feel them then.