The other day, I ran into a friend walking her dog. As we chatted, the dog started licking its front feet. My friend said she’d been licking them for a few days and asked what I thought might be the cause. Well, that’s like asking what kinds of fish might be in the Pacific Ocean – there are so many options, it’s hard to know where to start.
The most common causes of a dog licking or chewing his feet are, in no particular order of likelihood: food allergy, yeast or bacterial skin infection, environmental/ seasonal allergy, contact with chemicals or other irritants, behavior (compulsion, attention seeking,…), pain in the soft tissue or bones under the skin, mites, cuts or abrasions, etc. Whew!
You can see why it’s important for a veterinarian to have a good game plan to wade through all these possibilities. Every vet is different; but I like to start with:
- A good history from the owner: Do other dogs (or humans) in the house have a related problem? When did this episode start? Has it happened before? Has the behavior or the look of the feet changed over time? Is it always limited to the front feet? Has the dog come into contact with any chemicals? Has there been any lameness? Has anyone tried to treat the problem?
- A thorough physical exam: I’m concentrating on pain in the feet; evidence of chronic licking/chewing (thickening of the skin, traumatic hair loss, staining from saliva, etc.); signs of licking/chewing elsewhere on the body; signs of trauma, tumors, or foreign bodies on/under skin of the feet; fever; and involvement of regional lymph nodes.
- Surface (dermatologic) testing: scotch tape test, hair pluck, skin scraping, and Wood’s lamp exam. Together, these help to determine whether there are excessive bacteria, yeast/fungi, or mites. I can culture the scrapings, too, if I need information about species.
- And perhaps radiographs (x-rays): if pain is evident in the foot/feet, I might take radiographs to find out if something is wrong with the bones or soft tissue beneath.
Now we come to a crossroads. If our plan has diagnosed and cured a disease process, great! If not, we’re headed into the dreaded allergy/behavior vortex. So, hold onto your seats – it’s likely to be a bumpy ride.
When everything else has been ruled out, and I am left with allergies or behavior, I try to rule out allergies first. I say “try” because this can be a lengthy and often unrewarding task. There are three broad categories of allergies in the dog: flea, food, and environmental/seasonal (referred to as “atopy”). Conventional wisdom holds that food-allergic dogs are usually also allergic to fleas, and that atopic dogs are usually also allergic to fleas and their food. This “allergy pyramid” suggests a path to a diagnosis: first we rule out the more common flea allergies, then food allergies, and finally, atopy. Sounds simple enough. It’s not.
To diagnose flea allergies, we use a topical flea treatment every three weeks for a few months. If the problem clears up completely, we may be done. Except for two small problems. First, itchy front feet are not typically due to flea allergies, which usually presents with “hot spots” or scabs on the back half of the dog. Then there’s the possibility that the primary cause is actually seasonal. In other words, what if the dog is primarily atopic, but the offending allergens went out of season during our flea treatment? All we can do is keep up the flea treatment until next year and see if the problem returns.
Food allergies are a bit more challenging. To begin the diagnosis, the dog will need to go on a special diet for 8-12 weeks. He cannot be given anything other than the special food. No treats. No flavored medicines. No poultry toothpaste. Nothing. This is often an emotional and practical challenge for owners. Some people live to give their dogs treats. Others have young kids, who may not be able to follow the “nothing else” rule. And some dogs simply will not eat any special diet that’s given. But, let’s say that, between the flea treatments and the special diet, the dog’s licking/chewing is under control. That’s wonderful! Nevertheless, we now need to “challenge” the dog with the old diet; only if he relapses can we confirm food allergies. Then there’s the seasonality issue again – we’re going to have to wait until next year to be confident of our diagnosis.
What if we still have to consider atopy? Diagnosis is typically made via skin testing or a blood test, both of which give some information on the most likely allergen culprits. These tests are good – but not perfect; some dogs slip through the diagnostic cracks and others are incorrectly labeled “atopic.” Still, if the dog has positive test results, a treatment plan should be developed. Some owners opt for “allergy shots,” called hyposensitization. Others (usually small dog owners) prefer medications like cyclosporine (Atopica), which reduce the dog’s immune response to the allergens; these meds are very expensive and their cost is directly related to the weight of the dog. Other drug options include some combination of antihistamines, steroids, fatty acids, and tricyclic antidepressants.
If no diagnosis has been made at this point, either something was missed – or it’s likely a behavioral problem. The good news is that there are board-certified animal behaviorists out there just waiting to help.
This discussion is by no means an exhaustive list of causes of and diagnostics for itchy feet in the dog. Rather, I hope it provides enough background information that a pet owner can have an informed conversation with his or her vet about the problem.