Lymph nodes usually become swollen in response to an illness or infection, with infection being the most common cause of swollen lymph nodes, states MedicineNet. Swollen lymph nodes in the neck may indicate an infection or illness located in the head, mouth, neck or throat, according to Healthline.
Lymph nodes are glands that store white blood cells and circulate lymph, which is a clear fluid that moves through the lymphatic system, states Healthline. If there is an infection or illness localized in a certain part of the body, such as the head or neck, the lymph nodes in that area may become inflamed and swollen. When bacteria, viruses or diseased cells pass through the lymph nodes as a response to this infection or disease, they begin to accumulate there. That is why lymph nodes sometimes swell up and become sore to the touch.
If the lymph nodes in the head and neck are swollen, it is likely in response to an upper respiratory infection such as the common cold, a sinus infection or laryngitis, states Healthline and MedicineNet. However, it could also be in response to a scratch or wound near these glands, an infection, or a tumor in the mouth, neck or head, states WebMD.
More serious conditions such as cancer can cause the lymph nodes to swell, as well as adverse reactions to medications and sexually transmitted infections, says Healthline. If the lymph nodes have been swollen and painful for more than a few days, see a doctor.