If the icky brown stuff is not effective in preventing your dog from licking and biting his paws, than something taken internally is probably necessary depending on the cause for the licking and biting. Biting paws is often a symptom of allergies. If the allergen causing the paw biting can be identified and eliminated than medication would not be necessary. Eliminating the allergens is often impossible because the allergens can be something ubiquitous in the environment, such as pollen's, dust mites, etc. Since identifying allergens can be very difficult and costly, medication is often just easier and less expensive. Prednisone, Temaril P and Atopica are all good medication choices for allergies.
I agree with Dr. Cheng that foot licking is often a symptom of allergies in dogs. The allergy can be to food, or to environmental allergens such as pollen, grass or dust. Additionally, secondary bacterial or yeast infections often develop between the toes, causing the itching and licking to worsen, so evaluation by a veterinarian for miscroscopic analysis of the inflamed feet is needed to evaluate if antibiotics are needed. The diagnosis of food allergy is actually fairly simple and inexpensive: feed a hypoallergenic diet for 6-8 weeks without any other treats, table scraps, rawhides, milkbones, or other foods, and if the symptoms resolve then the diagnosis is food allergy. There is no accurate skin or blood test for food allergy in animals. The treatment is to continue the hypoallergenic diet. When choosing a hypoallergenic diet it is important to pick a food that has one protein and one carbohydrate that the dog's immune systemic has never been exposed to before, such as rabbit/potato, fish/sweet potato, etc. The best hypoallergenic diets are home cooked or prescription and your veterinarian can help you with that choice. There are a few over the counter diets that are also limited ingredient, such as Natural Balance or Solid Gold, but make sure to read entire ingredient labels, as some foods contain alot more than the front of the bag claims.
If foot licking persists despite the hypoallergenic diet and clearing up secondary infection, or if the symptoms only occur during certain seasons, then the diagnosis by exclusion is atopy, or pollen, grass and dust allergies. Options for treatment of atopy include treating symptoms with medications (antihistamines, weekly oatmeal baths, daily wipedowns of the feet, and yes, occasional anti-inflammatory medications such as prednisone, Temeril-P or Atopica) can be helpful, but you need to discuss the potential side effects of these stronger immunosuppressive medications with your veterinarian before using these drugs long term. Additionally, although Atopica is a better choice than steroids for long term use, it can cost hundreds of dollars per month for a large dog. In dogs that the milder therapies don't help, and that need long term steroids or Atopica, evaluation by a veterinary dermatologist (www.acvd.org) for allergy skin testing and desensitization injections can identify and treat the cause of the itching skin and feet, rather than just treating the symptoms with medications.
Kimberly Coyner, DVM DACVD
Dermatology Clinic for Animals of Las Vegas
An alternative is to buy a couple pairs of white cotton baby socks at Walmart for example and put them on your dogs feet. This has proven to be cost effective and helpful to keep the allergens from affecting your dogs feet. You can also get a pint sized squirt bottle and fill it 2/3 with distilled water and 1/3 with alcohol and shake to mix: when he comes inside spritz his feet and dry them to remove topical allergens. Chlorpheniramine maleate 4mg tablets are an inexpensive anti-histamine that are also helpful to temporarily relieve licking, along with the socks. I do agree that feet licking is a sign of Atopy (lack of internal immunity) and is a lifelong situation that must be managed. Boosting your dogs internal immunity is a valid long term consideration.
Dr Carol Osborne, DVM