Lymph nodes play an important part in the body's defense against infection. Swelling might occur even if the infection is trivial or not apparent.
Update Date 2/24/2016
Updated by: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.