Why is my dog licking his leg spots?

Q: Oscar, my 14-year-old male medium-size crossbreed dog, has started licking two spots on his front left leg. Why could this be, and is there anything I can do?

BRYON LOWRIE, Ponteland A: The most common cause of dogs licking their legs or paws is atopic dermatitis. This is due to an allergy causing itchy skin. Presuming Oscar has never been a dog that licks his paws and this is a habit that has started relatively recently, I suspect pinpointing the cause for Oscar will require a closer veterinary examination. Repeated licking of the leg, particularly in an older dog that is likely to have poorer oral hygiene, may lead to infection. This infection can lead to a nasty circle of infection causing irritation, which causes licking, which introduces more infection, which causes further irritation, and so on. If this is the case, your vet may be able to prescribe some antibiotics to treat this underlying infection. Another cause of this licking could be pain from an underlying arthritis, with the spots being due to an infection secondary to the licking. In this case your vet may want to X-ray the area to see if there is any evidence of arthritis or possibly trial some painkillers to see if this improves the behaviour. Tumours are also a possible cause of the licking. Mast cell tumours, in particular, can cause a dog to be itchy and the spots may be a sign of this. If your vet is suspicious of this they may want to take a biopsy to exclude this as a possibility. Early diagnosis and surgical removal of a mast cell tumour is often curative so it is certainly worth getting this licking behaviour checked out by your vet and the spots examined.