Itch-And-Scratch-Bite-And-Lick!
By: T. J. Dunn, Jr. DVM
If your dog is continually scratching, biting and licking at itself, and is driving you crazy with its self-absorbed antics, take comfort. You are not alone.
This article will explain the six major reasons why dogs and cats will itch and scratch. The bottom line is... don't let them suffer! There IS a diagnosis to be made and then you and your veterinarian will be better able to select the proper treatment plan.
Itching and scratching in dogs:
One of the most common calls made to any animal hospital in America goes something like this: “Doctor, I’ve got to get this dog in right away. He’s driving us nuts. All he does is itch and scratch, bite and lick and he’s keeping us up all night!” My thought is that if the pet’s caretakers are being driven “nuts” by the dog’s scratching and licking, how awful must the poor dog feel? This kind of call to the veterinarian refers to a fairly serious case of pruritus (pruritus means itching). In reality there is a wide spectrum of causes and severity of pruritus in dogs with skin and coat trouble. Some dogs can spend hours romping through fields, digging holes, and rolling in the grass and still have no after-effects at all. Others, kept indoors and fed an excellent diet, may have severe skin disorders. Let’s see if we can make some sense of this complicated and aggravating situation and try to answer the question “Why does my dog itch-and-scratch-bite-and-lick?”
Environmental Dermatitis - Patients in this category are physically and nutritionally normal, but present with signs of pruritus, hair loss and skin irritation. By careful discourse with the owner regarding diet, activity, medical history and environment, and by performing a thorough physical exam, the veterinarian can rule out the other categories of dermatitis. Through the analysis of the patient’s history, the veterinarian will discover that the patient spends time swimming or excavating gopher holes or romping through fields where thistles seem prevalent. Many dogs are very sensitive to simple lawn grasses. And by matching what is visible on the patient’s skin with a probable environmental irritant - the cause of the skin problem can be determined and corrective measures taken. An example is Moist Eczema, often called a "Hot Spot". These skin lesions often occur as a result of moisture on the skin surface from rain, pond or lake water. Minute scratches on the skin from, for example, a clipper blade, may trigger other cases. Especially in dense coated dogs or dogs where there is an accumulation of mats or shedding hair, moisture on the skin may remain long enough to allow superficial bacteria to reproduce (sort of like an organic soup!) and create an infection. Some cases of Moist Eczema will spread very rapidly and require rather aggressive therapy to correct. Contact with plastics can create ”Environmental Dermatitis”.
Nutritional Dermatitis - Correction of these cases should be a “no brainer”, but even today, many veterinarians and pet owners really believe the “Complete and Balanced” statement on pet food labels. Unfortunately, many dogs and cats live their entire lives in less than optimum health because their caretaker feeds the least expensive food they can find… and feels secure in doing so because of that “Complete and Balanced” statement.
In my thirty-five years of practice, I have seen hundreds of dogs and cats whose lives changed dramatically, and where the pet’s caretakers were shocked and surprised at the remarkable difference in their pets, by the simple act of providing the pet with a high quality, meat-based diet. Look at Nutrition for some common sense information about sound feeding principles. Take a look at the photo of a dog in less than optimum health that has been eating a “Complete and Balanced” diet for years. Without proper nourishment this dog’s entire body, not just its skin and coat, will be continuously in a state of stress. High quality, (more expensive!) meat-based dog foods seldom, if ever, create the kind of skin and coat seen in the photo above. If you feed dry commercial dog food, be certain that the first ingredient listed is meat such as beef, poultry, lamb or fish.
Will supplements help? Absolutely! But if the diet is a high quality, meat-based brand, the need for supplements is much less critical. It has been my experience that supplements such a Omega Fatty Acids, Vitamins and table scraps will always help a dog that is eating a generic, commercial dry dog food; and on occasion, supplements may even show positive benefits in a dog eating a high quality diet. Many types of dermatological problems are avoided if the dog or cat is consuming an optimum diet. In some cases, adding a supplement such as DermCaps, a popular Omega Fatty Acid supplement with a number of beneficial ingredients, is the key factor in avoiding repeated episodes of Hot Spots and other skin afflictions.
Parasitic Dermatitis - The most common response a pet caretaker makes when they see their dog scratching and biting at itself is “I think he’s got fleas”. And sometimes this guess is correct. Dark, copper colored and wingless, and about the size itchfleas of the head of a pin, fleas are big enough that they can be seen scurrying along the skin surface trying to hide within the sheltering forest of fur. There are a number of highly effective and safe flea preventatives your veterinarian can prescribe. Fleas are ubiquitous, but an understanding of their life cycle, where they hide in the dog’s environment, and utilizing modern pharmacology breakthroughs, no dog needs to be “driven crazy” with pruritus, hair loss, scabs and infections as a result of flea infestation. Repeated exposure to fleas can trigger a hypersensitivity (an abnormal, excessive reaction) to the bite of even a single flea. Every veterinarian has been fooled into making a diagnosis of “allergy”, not even suspecting fleas, simply because no fleas were discovered at the time of the physical exam. This is a classic example of a Parasitic Dermatitis (flea bites) triggering a complicated Allergic Dermatitis (due to the flea saliva).
Interestingly, the all-too-common tick rarely triggers pruritus or allergic reactions, but on occasion will leave an ulcerative lesion that is notoriously slow to heal.
Chiggers, deer flies, and gnats (sometimes called No-See-Ums) can be considered nuisances and generally do not create remarkable systemic skin problems. Local treatment with first aid ointments generally is successful.
Cheyletiella mites look like tiny spiders under a magnifying glass and are often called “Walking Dandruff” because upon close inspection it seems like little flakes of dry skin are actually moving about. Partly because they live on the surface of the skin, these tiny critters can be eliminated easily by using any common flea shampoo. And here’s a creepy thought… Cheyletiella mites can be transmitted to humans where they create, just like on the dog, alopecia (hair loss) with a dry, flaky, slightly pruritic skin surface.
Sarcoptic mites are nasty critters! Also called scabies or red mange, they create very intense pruritus, alopecia, and inflamed skin with multiple small scabs often present. Sarcoptic mite infestation, more than any other entity, is frequently misdiagnosed as Allergic Dermatitis by even very competent and experienced veterinarians. Many veterinary dermatology specialists will not accept an uncontrolled “Allergic Dermatitis” referral case unless the referring veterinarian has first ruled out Sarcoptic mites by actually treating the dog for scabies. Do as many skin scrapings as you like, you’re not going to find these little rascals because, unlike most skin parasites, these burrow right down into the skin. (Even ticks simply hold on to the surface of the skin while they feed; ticks do not burrow into the skin.) Unfortunately, many dogs are treated with cortisone for a supposed allergic dermatitis when in fact these Sarcoptic mites are the cause of the pruritic, inflamed skin... the unnecessary cortisone eventually worsens the situation.
Sarcoptic mites happen to have preferences… certain types reproduce and thrive on dogs, but they do not thrive on other species such as humans. Nevertheless, Sarcoptic mites from dogs can infest humans so if your dog has signs of scabies and you are itching and have little scabs, make sure you see your dermatologist (MD, not DVM)! Mention your concern about scabies mites. If your physician makes a diagnosis of scabies on you, your next call should be to the veterinarian to make an appointment to discuss the possibility of Sarcoptic mites in your dog… (the one that’s been getting all those cortisone shots for “allergy”).
Then there are Demodex mites - also called “mange”. These little rascals do live and reproduce just under the skin surface in the tiny hair follicles and oil glands of the skin. Unlike Sarcoptic mites, Demodex mites can be seen on a skin scraping viewed under the microscope. They look like tiny cigars with stubby legs stuck to the front half of their body.
Demodex is most commonly seen in young dogs. In adult dogs, Demodex cases seem to be associated with individuals that are stressed from disease, poor nutrition, immune disorders or a harsh environment. There is evidence that many cases of Demodex have a genetically transmitted immune protein deficit underlying its manifestation; the dog’s breeder should be informed of any cases of Demodex mites. If the dog is otherwise healthy, there are effective treatment protocols for Demodex. On the “itch scale”, Demodex causes very little pruritus. On the “baldness scale” Demodex creates mottled and patchy alopecia.
Infectious Dermatitis - Bacterial, fungal and yeast organisms are notoriously obnoxious skin and coat pathogens. Fungal organisms are called dermatophytes. One type, called Microsporum canis, causes non-pruritic, circular patches of hair loss, often called ringworm. Transmissible to other dogs (and occasionally some strains of fungi can be transmitted to humans) your veterinarian can diagnose and treat skin fungal infections in the office.
Yeasts, most notably a common contaminant of inflamed and environmentally stressed skin called Malassezia pachydermatitis, can irritate an already diseased skin surface. Especially notorious for creating long term, low-grade external otitis, Malassezia does cause pruritus and inflammation. Yeast infections typically create greasy, odorous and pruritic signs in affected dogs. The skin is stressed by the waste products of the organisms and responds by releasing histamine - which triggers further inflammation, pruritus and cell damage. If a yeast infection is diagnosed, there’s generally something else going on such as Hypothyroidism, chronic administration of cortisone medication or dietary fatty acid deficiency.
Bacterial dermatitis rarely occurs spontaneously. Normal healthy skin has tremendous numbers of a variety of bacteria present all the time. If something upsets that balance, such as antibiotics eliminating one or two types, the remaining types have a free-for-all! Anything that damages the normal, healthy, intact skin will hamper the skin’s defense mechanisms. Any Environmental Dermatitis, such as contact with grass, plastic, an abrasion or moisture, can adversely affect the skin’s defensive barriers and opportunistic bacteria then have their way. Parasitic damage to the skin will allow invasion by bacteria and trigger the body’s healing defense mechanisms.
A common affliction of dogs, Infectious Dermatitis often is so irritating that dogs will lick continuously at the lesion and undo any healing that has taken place. A moist, sticky, inflamed skin lesion along with hair loss is characteristic of bacterial dermatitis. These can spread rapidly and even be transposed to other areas of the skin through biting, licking, and scratching of previously uninfected areas. Lipfold Pyoderma, as seen in the photo on the left, is a classic example of chronic infection affecting the skin.
The treatment for Infectious Dermatitis often includes clipping the hair from the area to allow the air to assist drying. The application of gentle topical medication is helpful as is the administration of oral antibiotics to fight the organisms that are deeply invading the skin. Yes, cortisone may assist in alleviating the stinging or itchy sensation, but may also suppress normal healing processes. Whenever an infection is present, the decision to use cortisone needs to be very carefully evaluated. A better choice may be antihistamines orally.
Allergic Dermatitis - 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 to 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 the dog going 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 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 disorder 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 pruritus. 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 a diagnosis 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.
Neurogenic Dermatitis – 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. 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.
In summary, keep in mind that any dog whose skin and coat are not in optimal health needs attention because that dog surely does not feel well. Be patient with your veterinarian because each category of “Dermatitis” must be evaluated, categories need to be ruled out, and a final diagnosis needs to be established BEFORE proper, effective treatment begins. Expect laboratory work, skin scrapings and blood tests to be required to reach that diagnosis.
If your dog is suffering from Chronic Dermatitis, all is not hopeless. Be persistent in trying to identify the cause and then pursuing a treatment. These experts work with severely affected patients on a daily basis and can be an excellent resource for assistance to those poor dogs that seem incessantly to itch-and-scratch-bite-and-lick. Resolving these cases invariably puts a smile on the veterinarian’s face, the pet owners face, AND the dog’s!
Canine Skin
Introduction
Skin is a wonderful invention -- it guards against dehydration by preventing fluid loss; protects man's best friend from exposure to the weather by presenting a tough surface to the outside world and providing follicles for hair growth; and makes pets huggable.
Skin is the body's largest organ -- without it, hair would have no place to grow, internal body parts would become external body parts, and people would not want to hug and stroke their pets.
Skin is both tough and elastic. It is moist on the inside, relatively dry on the outside. It helps regulate Sparky's body temperature through the blood vessels and reduces exposure to extreme cold by muscular action that fluffs the hair and traps heated air next to the body.
In short, skin is a wonderful invention.
Skin comes in three layers: epidermis, dermis, and panniculus. The epidermis is the body's environmental shield made up of tough keratinized cells glued together in stacks by fats. This layer is constantly replaced; the glue dries out, the outer layer of cells sloughs off and new cells rise from the basal cell layer of the epidermis, elongate, and harden to keep the horny outer layer intact.
The epidermis is a barrier against injury, disease, and damage from ultraviolet light. Obviously, the horny layer protects the internal organs from exposure and massive fluid loss. The ability to quickly replace a damaged epidermis is critical in mending trauma, particularly in cases where burns, abrasions, or cuts leave the body vulnerable to infection and dehydration.
The chief guardians against infection that penetrates the skin's horny outer layer are the amoeba-like Langerhans cells that capture foreign proteins (antigens) and send them on the road to destruction. If the Langerhans cells are overzealous in their work, the dog can develop an allergy -- a intensified immune response to a common substance.
Skin protects dogs from ultraviolet rays of the sun by providing a foundation for the haircoat and by producing melanin to color hair and skin. Melanin is a natural sunscreen. Humans can increase the production of melanin by repeated exposure to the sun, but dogs do not tan.
Inner skin
The epidermis is joined to the dermis at the basement membrane, a layer of collagen and other products of the basal cells. Collagen is a tough, durable, fibrous protein that makes up 90 percent of the dermis and provides strength to the skin. How tough? Tanned collagen from cattle skin is otherwise known as leather.
Collagen occurs in bundles. Between the bundles are the skin's “rubber bands,” the elastin cells that help provide skin flexibility. The third component of the dermis are glycosaminoglycans molecules composed of sugar and protein. These cells keep the skin layer moist.
The cells of the dermis provide a framework for blood vessels to bring oxygen and nutrients to the skin and nerves to help the dog react to and interact with his world.
Blood vessels in the dermis help control Fido's body temperature. When he runs and romps and builds up body heat, the blood flow to Fido's skin increases to release the heat to the environment. In cold weather, blood flow to the skin dwindles to keep the heat where it does the most good.
Under the dermis is the subcutaneous fatty layer that has two widely disparate jobs as protective shock absorber and food storage locker for certain vitamins and energy bits called lipids. Hair follicles rise from the dermis layer.
Do dogs sweat?
Yes and no. The dog's dermal skin layer has two types of glands that produce fluids. The apocrine glands, which produce sweat in humans, have two other functions in dogs — they help seal the outer layer of the epidermis and they secret pheromones that give dogs a distinctive body odor. The eccrine glands in the pads of the paws do produce a watery secretion similar human perspiration. This secretion leaves damp pawprints behind nervous or stressed canines and may also improve traction for a quick getaway.
Skin diseases
The skin is subject to attack from without and from within. Injury from foreign objects, licking tongue, nibbling teeth, or scratching feet, ambush from external parasites, and assault from internal infections or autoimmune deficiencies.
Inhalant and contact allergies are common causes of skin irritation that can develop into more serious problems if Sassy digs and bites at her skin. Hot spots, hair loss, skin inflammation and crusty lesions can result from constant bothering of the skin.
Allergies are the result of an overactive immune system that releases histamines in its effort to cleanse the body of foreign proteins from pollen, dust mites, or other materials. The histamines cause the itching.
Some dogs react well to one of the over-the-counter anti-histamines such as Benadryl, Tavist, Seldane, or Chlortrimeton. Atarax, another anti-histamine, is available by prescription.
Some dogs need stronger medication to break the itch cycle. Veterinarians may prescribe a steroid drug such as prednisone to depress the immune system so that histamines are not produced. Steroids have several potentially serious side effects, so should be used sparingly and only under veterinary supervision.
Some dogs develop lesions as a result of constant scratching. These lesions can become infected and require antibiotic treatment.
Skin parasites
Mange mites, fleas and ticks and can cause disease in dogs. Demodectic and sarcoptic mange mites live under the skin and cause irritation and hair loss. There is some suspicion that susceptibility to demodectic mange mite infestation is inherited because the disease manifests in puppies and dogs that may have compromised immune systems. Most affected puppies do recover and have no immune deficiency; those puppies that continue to be affected by the mites may have impaired immune systems.
Sarcoptic mange (aka scabies) drives dogs crazy with intense itchiness. This mite burrows under the skin to lay its eggs. Some dogs can harbor the mites without reaction, but others develop a severe allergy to the presence of these spider cousins. This mange can seriously debilitate an affected animal. and even cause death.
Mange can be treated with ivermectin (except in Collies, which seem to have a severe reaction to this pesticide) or with various types of insecticide dips.
Some dogs become allergic to flea bites, making flea control an important part of the family's dog care plan. One flea can cause a reaction in a sensitive dog. Fleas are also vectors for tapeworms. However, the wide variety of flea treatments available — both organic and manufactured insecticides and genetically engineered natural controls — provides an appropriate choice for all pet owners.
Ticks don't hang around long enough or bite frequently enough to cause major skin problems, but they are vectors for Rocky Mountain Spotted Fever and Lyme Disease that they can transfer to dogs through their bites. Ticks are more difficult to kill than fleas and there are no organic or biological controls for these spider and mite kin. The best preventive is to examine the dog after he has been in fields or woods, remove any ticks, and place them in a vial of alcohol.
Immune deficiencies
Canine autoimmune diseases can cause skin problems ranging from loss of hair or pigment to blindness. The immune system malfunction that allows these diseases to develop may be inherited, although related dogs may have different diseases.
Autoimmune skin diseases are still rare but seem to be increasing in occurrence. Some of them seem to be breed specific. For example, Collies, German Shepherds, Shetland Sheepdogs, and Siberian Huskies are particularly susceptible to discoid lupus erythematosus, the most common autoimmune disease of the skin. Akitas, Chows, Dobermans, Newfoundlands, Bearded Collies, and Dachshunds seem to be most vulnerable to Pemphigus foliaceus, a disease in which skin breakdown causes thin blisters to appear mostly on the face, nose, lips, and ears. Akitas, Samoyeds, and Siberian Huskies are the most frequent victims of VKH, a rare autoimmune disease that causes loss of pigment in lips, nose, and eyelid margins and whitening of facial hairs. The eyes can be affected, and the dog can become blind.
Treatment for autoimmune diseases involves the use of steroids or other immune system suppressers, carefully balanced to control the disease without opening the door to infections. Dogs can be made more comfortable with medicinal baths with shampoos recommended by the veterinarian.
Skin, skin, glorious skin
Healthy skin is a reflection of the general health of the dog. A bright, shiny coat, smooth skin, and normal body odor trumpet a dog's condition to all who watch him romp and play or recline by the fire on a winter evening. Owners who put their hands on their pets quickly notice changes in the skin and can take steps to remedy any problems.
Dry skin from winter heat? Add some Vitamin E and omega oils to the diet. Dull coat? Watch for signs of depression or illness. Afraid he's going bald? Check with the veterinarian to discover the reason for hair loss. Think she'll chew right through her paws or rub her nose raw on the carpet? As the veterinarian about inhalant allergies.
The skin, the first line of defense, does its job well, but it sometimes needs a boost, so the wise dog owners monitors his pet's skin condition.
By: Norma Bennett Woolf
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