Question

What do lymph nodes do? Why do they sometimes become swollen?

Answer 1

Lymph nodes act as the first defense for your immune system. When you are sick, they become enflamed which then becomes swollen.

Answer 2

I think lymph nodes produce white blood cells...so when you get sick, they produce many white blood cells to fight the bacteria or virus, and I assume they swell because they're over-producing white blood cells.