Swollen lymph nodes: When to watch and when to worry
9/29/2025 by Tyler Benning, M.D., M.S.
Swollen lymph nodes are common in children, especially toddlers and young school-aged children. Viral or bacterial infections often cause swollen nodes, but in rare cases, they can be a sign of more serious conditions, like blood cancers (leukemia and lymphoma) or an autoimmune disease. This article will review the function of lymph nodes and common causes of swollen lymph nodes.
What are lymph nodes?
Lymph nodes are small tissue clusters that house many of the body's immune cells. Lymph nodes detect pathogens like bacteria, viruses and fungi, and they activate specific immune cells to fight off invaders. Lymph nodes are found throughout the body, with large clusters in the head, neck, armpits and groin. When lymph nodes detect an invader, they can grow and become tender.
What are the common causes of swollen lymph nodes?
Common viruses and bacteria cause many swollen lymph nodes. Children with infections like the common cold or strep throat frequently get swollen head and neck lymph nodes. In other cases, the lymph nodes may become infected with bacteria, and your child's clinician may need to prescribe antibiotics to treat an infected lymph node.
If my child has a swollen lymph node, should I be worried?
Some parents worry that swollen lymph nodes could be a sign of blood cancer, like leukemia or lymphoma. The vast majority of swollen lymph nodes are not caused by blood cancer. However, there are some warning signs that parents should watch out for. A swollen lymph node is more concerning if the child has had weight loss, drenching night sweats or a fever for over seven days. Larger lymph nodes (greater than or equal to 2 cm) and lymph nodes located just above the collarbone are also more concerning.
Most swollen lymph nodes disappear with time, though additional lab tests or imaging are sometimes needed. Some swollen lymph nodes require antibiotic treatment. If you note a new, enlarged lymph node, please get in touch with your child's primary care clinician to determine if your child needs to be evaluated in the clinic.
Tyler Benning, M.D., M.S., completed his pediatric residency at Mayo Clinic in Rochester in June 2025. He started his pediatric hematology/oncology fellowship at the University of Minnesota in the summer of 2025.