SYMPTOM
Swollen lymph nodes
Owners may observe swollen lymph nodes in their pet.
Various conditions
This symptom can occur in multiple conditions and warrants further assessment.
Reactive Lymphadenopathy From Local Infection
Nodes draining an area of infection, such as dental disease, a cat bite abscess, or a skin wound, enlarge as they respond to the immune activity fighting that infection, most often affecting the submandibular nodes under the jaw or those near an infected limb. This is one of the more common and self-limiting explanations, with the swelling typically easing once the underlying infection resolves. Outdoor cats with a history of fighting are more frequently affected due to bite wound infections.
Retroviral Infection (FeLV And FIV)
Feline leukaemia virus and feline immunodeficiency virus alter immune function and can cause generalised lymph node enlargement, either from the infection itself or from secondary illnesses it predisposes a cat to. Cats with outdoor access and unresolved territorial disputes are at greater risk of exposure through bite wounds and prolonged contact with infected cats. Widespread, symmetrical node enlargement is more typical of this pattern than swelling confined to one area.
Lymphoma
This cancer of lymphoid tissue can cause firm, non-painful, generalised lymph node enlargement, and in cats it is associated with both older age and, in a smaller proportion of cases, earlier FeLV infection in younger animals. Node enlargement from lymphoma tends to persist and gradually progress rather than fluctuating the way an infection does, and it is sometimes accompanied by weight loss or reduced appetite. Multiple body regions are often affected at once.
Bartonellosis (Cat Scratch Disease)
Bartonella henselae, transmitted between cats by fleas and passed to people through scratches or bites, can cause regional lymph node swelling, particularly around the head and neck in cats carrying a heavy flea burden. Kittens and young cats are more commonly affected, and the infection often causes only mild or no illness in the cat itself despite the node enlargement. Effective flea control reduces the likelihood of transmission and reinfection.
Why timing matters
Early observation
Early recognition allows prompt assessment and intervention if needed.
Later presentation
Persistent or worsening signs may indicate progression requiring attention.
The significance of this symptom depends on its context, duration, and associated findings.
Conditions commonly associated
Feline Leukaemia Virus (FeLV)
Lymph node enlargement may reflect lymphoma or immune activation from chronic infection.
Lymphoma in Dogs
Lymphoma often causes generalised or localised enlargement of lymph nodes, reflecting the proliferation of abnormal lymphocytes within the lymphatic system. In many cases, the swelling is painless and may be noticed during routine handling or grooming.
Dental Disease in Dogs
Dental disease can lead to enlargement of the submandibular lymph nodes beneath the jaw, as these nodes drain the oral cavity and respond to chronic bacterial presence and inflammation in the gums and teeth.
Dental Disease in Cats
Dental disease in cats may cause swelling of the submandibular lymph nodes due to chronic oral inflammation and bacterial activity, though this finding can be subtle and easily overlooked during routine observation.
Pneumonia
Pneumonia can cause enlargement of the tracheobronchial lymph nodes within the chest as part of the immune response to infection, though these are not palpable externally and tend to be identified through imaging rather than physical examination.
Atopic Dermatitis in Dogs
Atopic dermatitis may occasionally lead to peripheral lymph node enlargement, particularly in areas draining regions of intense inflammation or secondary skin infection, reflecting the immune system's response to ongoing allergic and microbial challenge.
Bartonellosis
Bacteria carried in from a flea bite provoke a response in the nearest lymph nodes, causing them to enlarge.
When to explore further
When the symptom is persistent or worsening
When other signs are present alongside
When daily activities or quality of life are affected
When there is uncertainty about the cause
Noting when this symptom occurs, any triggers, and how it changes over time can provide useful information for veterinary discussions.
Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS