Seborrhea Dermatitis in Dogs
Seborrhea is a common canine skin disease that is not contagious. It is similar to but more severe than human dandruff. There are two major types of seborrhea in the dog. “Seborrhea sicca” is a dry form of seborrhea in which dry scaling is the major sign. This is seen in Dobermans and Irish setters and may develop into a dry snowstorm of flakes. “Seborrhea oleosa”, or oily seborrhea, occurs with greasy crusting that is typical of Cocker spaniels. Seborrhea may or may not be associated with inflammation of the skin or dermatitis. An underlying disease such as allergies, hypothyroidism, dietary deficiency, or hereditary influences usually causes seborrhea. Technically it is believed that seborrheic dermatitis in dogs is caused by a defect in the manner the skin matures.
Once the clinical diagnosis is made, we must gain the cooperation and understanding of the disease from the client. Much time should be spent explaining that seborrhea is a symptom of a disease and that finding the underlying cause is the only way to cure the disease and cure the problem. Without this diagnostic effort, the pet is condemned to a lifetime of treatment without cure. Even with this effort, many causes cannot be found. However, the client may understand better that there is no cure, and although the pet will always have seborrhea, it may be controlled with the proper medications and therapies. These therapies are meant to control the signs but are not a cure for the disease.
Many times with dermatological diseases that are chronic, the client looks for a veterinarian who has a positive attitude and is enthusiastic about helping with these frustrating problems. If the veterinarian takes a defensive attitude (because he or she is frustrated with the lack of cure) the client may seek another more optimistic veterinarian. The ultimate control of many skin diseases is a trial and error effort that requires cooperation with both the client and the veterinarian.
Seborrhea literally means “flow of sebum” or “flow of suet”. The disease includes changes in sebum production as well as changes in keratinization and inflammation of the skin. Increased epidermal turnover is the hallmark of seborrhea. Causes include hormonal imbalances, allergies, fleas, mange, infections, and nutritional and environmental factors.
There are several seborrheic syndromes that are managed differently and are typified by certain breeds.
Doberman Pinscher Seborrhea
Presents as a young, adult dog with excessive flaking and scaling. This “dandruff” is distributed over the trunk, dorsal rump, and thighs. This “snowstorm of dandruff” which feels waxy on the fingers is associated with small, raised bumps along the back that look like hives. Small raised tufts of hair that may fall out leaving bald spots may be associated with these bumps. Itching is related to the degree of flakiness.
To diagnose seborrhea, rule out demodectic mange, hypothyroidism and bacterial folliculitis. Most cases have bacterial involvement, which appear as raised bumps. This pyoderma must be controlled. Antibiotics should be used for four weeks. Steroids should be avoided. External factors include environmental humidity, bathing and dipping. Normalization of the skin is the goal. Use a tar shampoo such as Allerseb-T® if severe, or milder formulas such as T-Lux® if not so severe. These should be used weekly. Moisturizing the skin is also important in the Doberman. Many methods or combinations may be tried:
- Humilac® spray.
- Bath oil applied with in a plant spritzer
- Humilac® spray added to dips (five capfuls per quart)
- Hot oil treatments
Adding oil to the diet is also beneficial:
- Corn oil, safflower oil, sunflower oil at 1 tbls per day to food
- Add Pro-zyme® or Viokase® to the food to increase fat adsorption
- Add Derm Caps ES® to the diet
- Feed Hill’s Science Diet® Performance®
Irish Setter Seborrhea
Presents with severe itching and extensive hair loss on the neck, trunk, extremities, and head.
The Irish setter may appear flaky, but the skin feels greasy to the touch. A strong “doggy odor” will be noticed by the owner. Papules, pustules, and redness of the skin are seen secondary to the itching the dog is doing. The ears have a ceruminous otitis externa. The itching that is seen may be so severe as to confuse it with sarcoptic mange. Pyoderma is common but is usually secondary to the itching that the dog does. This pyoderma should be treated first before the seborrhea is addressed. A re-evaluation in one month is necessary to allow the severity of the seborrhea to be seen. Corticosteroids should not be used until the bacterial disease is controlled. If the itching is still severe after the bacterial infection is controlled, then other causes for the itching can be explored.
Thyroid hormone levels should be tested. Allergy testing should be done if the dog is still itching after the antibiotics have been used. Flea control should be evaluated and sarcoptic mange should be considered. Recurrent pyoderma and seborrhea are common in the Irish setter. Topical medications are variable. Alternating Oxydex® shampoo with Allerseb-T® every five to seven days will give good results. The new oatmeal shampoo and rinses sold as Epi-Soothe® will also be helpful.
Cocker Spaniel Seborrhea
The seborrheic cocker spaniel presents as a middle age dog with a moderate degree of itchiness.
There is a significant degree of wax build-up and greasiness. The ears are often affected with chronic inflammatory ceruminous otitis externa. Large epidermal collarettes are seen as evidence of a bacterial skin infection secondary to the seborrhea. Scraping for mange and tests for hypothyroidism as well as skin biopsies are indicated for Cocker spaniels. Skin biopsies sometimes show changes typical of vitamin A deficiency. Retinoids should be effective in these cases. Treating the bacterial infection with topical benzoyl peroxide as well as oral antibiotics is important.
The greasy coat can be treated on an alternating basis with tar and sulfur shampoos – Allerseb-T®. Bathing is sometimes done on a daily basis until the skin is under control. Dietary changes such as the addition of fat to the diet can be tried. This is usually done by recommending Hill’s Science Diet® Performance® be fed if the dog is not too overweight. If the dog is overweight; feed Hill’s Prescription Diet® Canine w/d® with Derm Caps ES as the fatty acid supplement. Clipping the hair may also be effective in helping to normalize the skin and allowing for easier medication of the problem. Supplementation with vitamin E, zinc and vitamin A have all been reported to be effective and can be tried. If all else fails, corticosteroids are effective in the cocker spaniel, but they may make the bacterial pyoderma worse. Alternate day prednisolone at the lowest effective dose is recommended.
Hormonal Skin Disorders in Pet Animals
Hypothyroidism is the term used to denote low circulating blood thyroid concentration. Thyroid hormone is the hormone responsible for cellular metabolism. Cellular metabolism is the rate that a cell performs its functions. The function of skin cells is to provide a protecting and enclosing barrier for the body. Without adequate levels of thyroid hormone the rate of cellular reproduction is reduced. The quality and quantity of skin that is produced is changed. The normal cellular defense mechanisms of the skin are reduced. Hypothyroidism is called “the great imitator”. It is a disease that can mimic any other skin disease and is difficult to diagnose without a blood test for circulating thyroid hormones. Animals with hypothyroidism may be lethargic and have a “tragic” expression to their face. Low thyroid hormone can even cause allergies because the skin is not perfect – pollens can actually penetrate the skin through small defects in it. A rule of thumb is that any animal missing hair down its tail is suspect for hypothyroidism. Most hypothyroid dogs respond well to daily or twice daily thyroid supplementation of thyroid hormone. Periodic blood tests are used to determine the dose and frequency of administration. Most pets with chronic skin disease should be tested for low levels of thyroid hormone in the blood.
Cushing’s disease is hyperadrenocorticism. This is the excessive production of cortisol. It can also be caused by the excessive administration of cortisone to an animal. This is called iatrogenic Cushing’s disease. Cushing’s disease is more common in older pets. The typical signs vary from no signs at all to severe disease. Most common signs include increased drinking of water and excessive urination. Panting is common. Elevation of the liver enzymes such as alkaline phosphate and low eosinophil count may also be seen. Cortisol makes an animal feel good so many clients do not report problems until other more obvious signs occur. These include the signs of pot-bellied appearance and hair loss over the trunk that does not affect the head and legs. Calcium deposits may also be seen in the skin as well as other organs. Because cortisone causes reduced healing and immune function, chronic infections may be seen. The typical animal is an aging poodle that is almost bald on the trunk with a potbelly. There are two mechanisms for this excessive production of cortisone from the adrenal gland. One is a tumor of the adrenal gland and the other is a tumor of the pituitary gland. Adrenal gland tumors account for about fifteen percent of the Cushing’s disease cases. Pituitary gland tumors account for about eighty-five percent of the Cushing’s disease cases. The pituitary gland secretes a hormone called Adrenal Cortico-Trophic Hormone (ACTH) every morning. This hormone goes to the adrenal gland and tells it to make enough cortisol for the day. When the cortisol level is adequate, the pituitary gland will stop producing ACTH. Pituitary tumors are not typically large enough to cause overt brain disease. A screening test called the ACTH stimulation test is done to see if excessive cortisone is in the blood stream. This test is usually performed in the morning by collecting a blood sample. Then ACTH is given and another blood sample is collected two hours later. Once diagnosed, medication can be given to reduce the adrenal gland size or to inhibit the release of ACTH from the pituitary gland. If an adrenal gland tumor is diagnosed, surgery is usually recommended.
Allergies are a major cause of skin disease and owner complaints. All skin allergies have the same basic mechanism. The mechanisms are very complex and intertwined but a simple explanation is necessary when communicating with clients. The hallmark of allergy is itching. Itching is caused by the release of histamine into the skin by mast cells.
- All allergies are the result of exposure to a substance that is foreign to the body. This is called an “allergen”. An allergen may be the pollen of any plant, a drug, the venom of an insect, the fiber of a carpet, or virtually anything. Animals can become allergic to anything just as people can.
- The allergen must break into the body in some manner. This can be through breathing the allergen into the lungs, or by a flea injecting it under the skin, or by washing your hands in it every day, or by a dog eating the same food for year after year. The allergen eventually gets into the body and is recognized by the surveillance systems of the body to be “foreign”. Most allergens are breathed into the body as pollens in the air. They then get into the blood through the lung tissue.
- A reaction to the foreign antigen (allergen) develops which results in the development of an IgE antibody by the lymph node against the offending substance. Normally this antibody would attack the antigen and destroy it. In an allergic reaction however, the antibody becomes attached to a cell in the skin. Most defensive antibodies are made of the IgG type and do not cause allergic reactions. Other antibodies, IgA antibodies, coat the surface of the skin and the mucous membranes to provide local immunity as the first line of defense against bacterial invasion into the body. For example, intranasal vaccines stimulate IgA antibodies, whereas, injection vaccines stimulate IgG antibodies.
- The IgE antibody however, is made for an allergen and becomes attached to a mast cell located in the skin of the dog. Mast cells can be located anywhere, but they are more prominent in the skin of the feet, around the eyes, and under the arms and legs of the dog. Therefore, signs related to the dog scratching his face by rubbing on the carpet or sofa, chewing his feet or licking between his toes, or scratching under his arms are signs related to pollen allergies.
- Mast cells are responsible for most of the signs attributable to an allergic reaction. The IgE antibody acts as a trigger to cause the mast cell to cause an allergic reaction. The IgE antibody will rest on the mast cell surface causing sensitization of the mast cell to the allergen. The antibody is actually a receptor for that allergen, and if the allergen comes into contact with the IgE antibody on the mast cell, the mast cell will de-granulate.
- De-granulation means the granules in the mast cell will burst out of the mast cell. These granules contain the major substances that cause an allergic reaction. Histamine, serotonin, SRSA, bradykinin, MIF, Thromboxane A2, and complement are released into the tissues of the skin.
- When an allergic reaction in the skin occurs, several functions happen at once. The chemicals above all have different functions that serve in the itch reaction to follow. Histamine causes the blood vessels to be leaky, bradykinin stimulates nerves to tell the brain to scratch the area, and serotonin closes outflow blood. Other chemicals attract white blood cells into the area. The net effect of these chemicals is a red, inflamed (white blood cells), swollen (blood in but no blood out) area that itches (nerves stimulated). The itching causes scratching which causes more trauma to the area causing further mast cell de-granulation and more reaction.
- Containment of the allergen will prevent its spread to the rest of the body and halting blood flow out of the area accomplishes this. The area is contained to prevent spread of disease and to allow the white blood cells to accumulate in the area and do their job.
- Destruction of the allergen is the goal of the body and may be attempted by any of the white blood cell types. As a result of their action, much unnecessary damage will be done to the area. This is much like the firemen that tear the house down to put out a fire in the trash can. The macrophages will come in and clean up the mess afterwards and will pick up the inactivated antigens and carry them to the lymph node for interrogation. This will result in further refinement of the antibodies produced in the IgE format that attaches to the mast cells. This will happen during each reaction and will result in subsequent reactions being stronger than previous reactions. Thus, the allergy gets worse over time.
- The body is notified of the allergic reaction by the nerves in the area. These nerves happen to be itch receptors, and they will cause the pet to itch any area in which an allergic reaction is happening. This scratching will result in more mast cell de-granulation and more damage, more swelling, more cell death, more macrophages, more antibody formation and worsening of the allergy. This becomes an “Itch-Scratch Cycle” that is self-perpetuating. The same reaction occurs in humans as “hay fever” or other allergies. In humans, allergies to pollens cause respiratory signs of sneezing and congestion. These signs are caused by mast cell de-granulation as well. There are more mast cells in the human’s respiratory tract than in the dog’s. In the dog, there are more mast cells in the feet, face and underarms than in the respiratory tract. This is why pollens cause a dog to scratch its face and feet while pollen allergies cause humans to have hay fever. The location of the mast cells determines the symptoms of the disease.
- Treatment of allergies can be achieved by only three methods:
- Remove the source of allergen – fleas, diet, or environment.
Removal of the offending substance would be appropriate if the allergen was food or fleas or something that is relatively easy to remove. If the allergen is pollen in the air, then the task becomes more difficult.
- Suppress the itch with antihistamines or steroids.
Suppressing the itch can be done with either antihistamines or corticosteroids. Antihistamines such as Temaril or Benadryl are not effective unless given before the allergy develops. These work only to suppress histamine, which is only one of the offending chemicals released, by the mast cell. Antihistamines will sedate the dog and in this way reduce the tendency to scratch. There are certain newer antihistamines that have been shown to be effective in controlling itch in dogs. There is a trial and error approach to which one is effective and in general at least for now they are fairly expensive. Hismanal is the most used in this category of newer antihistamines for dogs.
- Hyposensitization to reduce the allergen reaction in the body.
Corticosteroids do suppress the allergic reaction at all stages before and after the allergy develops. The mast cells are stabilized and do not de-granulate and the mediators of inflammation and itch are inhibited. Corticosteroids are very effective but must be used correctly. NOTE: Flea Allergy Dermatitis is discussed in the Pillars™ Flea lectures.
- Remove the source of allergen – fleas, diet, or environment.