Swollen lymph nodes, also called lymphadenitis, occur in dogs due to a higher level of white blood cells caused by an infection in the body or a disease of the tissues, according to Vetinfo. There are several causes of swollen lymph nodes, such as allergic reactions, internal parasites, leukemia, autoimmune conditions, and viral, bacterial or fungal infections.
Lymph nodes are tiny glands found in different parts of the body, such as the neck, explains Vetinfo. They are responsible for filtering blood and storing the white blood cells or the lymphocytes. Autoimmune conditions happen when the dog’s body reacts negatively to its own cells, while viral, bacterial or fungal infections are usually transmitted from other pets or ticks and fleas. An abnormal growth on the lymph nodes or an injury within the lymph node area also causes the nodes to enlarge.
Vetinfo states that a dog with lymphadenitis usually has palpated and enlarged lymph nodes. Aside from the swollen appearance, other symptoms of swollen nodes in the neck area include difficulty in swallowing, difficulty in breathing, lack of appetite, nausea, vomiting and lethargy due to infection. A veterinarian typically performs a physical exam and several blood tests to diagnose the condition. Lymph node aspirates also help with the diagnosis. X-rays are necessary if cancer is a suspected cause and a biopsy may be necessary if there is a tumor.