Lymph nodes are small, bean-shaped glands that are part of the lymphatic system, a crucial component of your body’s immune defense. They filter lymphatic fluid, trapping bacteria, viruses, and other harmful substances. When your body is fighting an infection or inflammation, lymph nodes can become enlarged and tender as they work overtime. Common causes for swollen lymph nodes in the neck include colds, flu, strep throat, ear infections, or even more serious conditions like autoimmune diseases or, rarely, cancer. Therefore, the first and most important step when you notice persistently swollen lymph nodes is to consult a healthcare professional to determine the underlying cause.