I’ll be honest. There’s no way to cover this topic in one article. Veterinarians spend entire weekends and lots of money attending seminars on this topic alone! It is common, it can be lifelong, it is a challenge to diagnose, and once identified it can be resistant to attempts at treatment. All the other categories of dermatitis must be ruled out (especially those elusive Sarcoptic mites) before a diagnosis of Allergic Dermatitis can be made. Food ingredients, synthetic and natural fibers, medications and pharmaceutical products, plant material and even dust all can trigger an Allergic Dermatitis.
Even common bacteria on the dog’s skin can provoke an allergic reaction to themselves! These cases of sensitivity to normal resident bacteria are very challenging to correct. No matter what kind of allergic dermatitis afflicts the dog, the ultimate cellular cause of the inflammation and resulting "itch-and-scratch-bite-and-lick" activity has a common cause … the release of histamine from skin Mast cells, the deposition of antigen/antibody protein complexes within tissues, the dilation of some blood vessels and constriction of others, the release of toxic chemicals from broken intracellular structures, and chemical and physical irritation of sensory nerve endings.
To what are dogs allergic? Take a look around you right now. Odds are that your dog could be allergic to half-a-dozen different substances in the very room you sit; that doesn’t even include microscopic substances in the air you and your dog breath! Food, carpeting, blankets, dust mites, mold spores in the air, pollen, plastic food dishes, furniture stuffing and ornamental plants all have the potential to trigger an allergic reaction in your dog. Food allergies are so common that pet food manufacturers have invested millions of dollars in research, development, promotion and delivery of “antigen specific” diets to help in the therapy of dogs with food allergies.
How do allergies develop? Each individual’s biochemistry is determined by millions of genetic variables. On occasion, an individual’s various immune responses may over-react to a certain material and "learn" to recognize this substance in case of future contact with it.
The offending agent is called an antigen. Flea saliva is a good example of an antigen that triggers "flea bite" hypersensitivity. When an antigen makes contact with the dog, the dog’s immune defenses - all primed and ready for a fight since it has previously identified the antigen as an enemy - set to work to disarm the antigen.
Unfortunately, during the course of the battle (called an antigen/antibody reaction) side effects of the battle can cause tissue irritation, inflammation, swelling and cell destruction. That’s when we notice skin problems in dogs and when they go into the "itch-and-scratch-bite-and-lick" mode! There’s a biochemical war going on within the dog!
Immunologists have classified a number of different types of allergic reactions. Skin and blood tests are common methods of attempting to identify what the patient is allergic to. Probably the most common type of Allergic Dermatitis seen in dogs is Atopic Dermatitis. This situation is triggered by a number of antigens including inhaled substances such as molds, dust, pollens and other static and airborne microscopic organic substances.
Dogs with Atopy lick and chew at their paws (see photo on right) and scratch their face, eyelids and ears. This skin problem can be very troubling for dogs and frustrating for the owner. One minute the dog may look and feel normal, the next it will chew its paw or face raw from the intense itching and scratching. There is a new product available to treat Atopic Dermatitis in dogs called Atopica. For many patients, this medication has truly been a "life saver."
Treatment of Allergic Dermatitis includes topical medicated soothing baths, ointments and sprays. The use of oral antihistamines can neutralize some of the destructive effects of internally released histamine.
More effective in alleviating the discomfort of allergies is cortisone. This potent hormone, normally secreted by the adrenal glands, can be manufactured commercially. Numerous derivatives of cortisone are used in pill, injectable, spray, liquid and ointment form. Caution: If you are sent home with a prescription for cortisone, or your dog has simply been given "a cortisone shot to stop the itching," your dog may ultimately be worse off than before if the true diagnosis happens to be an unrecognized case of Sarcoptic mites!
Be patient, yes, but be persistent, too. If your dog is itching, scratching, and licking, or if the skin and coat are not healthy appearing, you and your dog need to diagnose what type of skin problem it is before treatment is started.
A key point to remember is this: There is no cure for allergies! All we can do is avoid the food, material or parasite that is triggering the immune response, desensitize the patient through immune modulation techniques, and assure that the patient is eating a high quality diet. There are a number of products that address allergies in dogs and allergies in cats that may help: Hypo-Allergenic Food, Hypo-Allergenic Shampoo, Hypo-Allergenic Dog Treats, Hypo-Allergenic Cat Treats, etc.
This group presents a major challenge to diagnose and treat. As a veterinarian I know I have classified a number of cases as "Neurogenic" simply because I have ruled out all the other categories! There’s nothing left but to blame the poor dog for all that incessant licking and chewing at itself! The most commonly seen form of Neurogenic Dermatitis is called Acral Lick Dermatitis, Lick Granuloma or canine neurodermatitis. Read more about lick granulomas by clicking here.
Although rarely seen in cats, in the dog something creates an impulse to lick at a specific area of skin. Characterized by persistent, obsessive licking and chewing at the target area, lick granulomas may have an unknown origin.
Commonly, though, most cases have a suspected cause such as boredom, separation anxiety, frustration, confinement, or even a minor physical origin such as a tiny abrasion that captivates the dog’s interest. The dog persists in traumatizing the area, which is usually confined to an easily accessible forelimb, carpus (wrist) or ankle area, and never allows the skin to heal.
Repeated episodes of self-mutilation, partial healing, then repeated trauma and healing, result in severe and disfiguring scarring. Deep bacterial infections are common and permanent skin damage results. A specialist in dermatology and a behaviorist may be the dog’s best friends in these cases of Neurogenic Dermatitis.