What is classed as a swollen lymph node ?

Depends on...: Whether or not a lymph node is called swollen depends on the size of the node and the average size of nodes in that part of the body, in people of that age group. A node about the diameter of a dime may be called enlarged, and one that is half the width of a dime is called normal sized. In children neck nodes usually get larger than dime-width in strep throat or other infections.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells and digested food. Lymph nodes "taste" the lymph for anything bad like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.