The most common skin disorder of older dogs is sebaceous gland (oil glands) tumors. These are very common, but 99.99% are benign and appear as oily warts. They can be a nuisance when in large numbers on small dogs, but are not life threatening. Surgical removal is usually recommended when they occur on the parts of the body where they interfere with function or might be traumatized enough to bleed as the lips, ears, around the eyes, between the toes, or any that the pet begin to lick or scratch excessively.
"Black Skin" Diseases is mentioned repeatedly on the Internet and in lay articles. Actually there is no such singular thing as "Black Skin" Disease. The black skin is a sign frequently seen in many skin disorders that result in hyperpigmentation (blackening) of the skin. The black pigment is melanin which is produced more rapidly and deposited in the skin in almost all of the hormonal disorders in dogs and in many other skin disorders that cause hair loss. As everyone knows, excess exposure to sunlight can cause one to tan. This is due to increased melanin being stimulated to protect the skin.
Cushing's Disease (CD) is commonly seen in older dogs and rarely in cats. CD is a result of over production of cortisone by the adrenal gland(s) of the body. A certain amount of cortisone is necessary for life but excess levels are deleterious. Cortisone production actually regulates our daily cycle. In most people and animals, cortisone production by the adrenal glands which are situated immediately above the kidneys, begins each morning a couple of hours before we normally awaken and serves as our trigger that it is time to get up. Cortisone production continues until it peaks between 10:00 AM and noon, then declines all day until it reach's a level whereby we become sleepy and go to bed. This cycle starts back the next morning.
Outdoor cats usually have a reversal of this cycle which makes them more nocturnal. CD causes the skin to become very thin and friable, especially in the cat. There is hair loss mostly over the truncal areas with the head and neck hair being spared. The hair that is lost is primarily the guard hairs and not all of the undercoat leaving a wooly texture. Untreated the undercoat is then lost and the skin hyperpigmentates excessively leaving a blackened skin.
Additionally, the excess cortisone causes marked muscle atrophy and increased fat deposition. This leaves the dogs looking very weak and pot-bellied. Left untreated they will later become diabetics. Although a serious disease, it can be diagnosed by multiple measurements of cortisone levels after giving a drug that blocks cortisone and then later a drug that stimulates cortisone production and can be treated successfully by your veterinarian. CD diagnosis and treatment is difficult and some veterinarians refer these cases to a specialist. Once treatment is instituted, the hair regrows and the black pigment resolves. Treatment is necessary for the rest of the dog’s life.
Hypothyroidism (low thyroid production) is more common than CD in dogs. It results mostly from the immune system of the dog building up antibodies against the thyroid tissue and rejecting it. Since the thyroid hormone is the hormone that regulates all the metabolism of the body, hypothyroidism can cause any sign or symptom in the book! Probably 50% will affect the skin and causes truncal hair loss and hyperpigmentation. Once diagnosed it is easily treated by daily replacement of thyroid hormone. Upon treatment the hair will re grow and the black pigment will resolve. Again, treatment is a lifetime commitment for dog and owner.
Hyperestrogenism (excess female hormone production) is less common now due to the increased importance put on spaying and neutering dogs. In female dogs it is caused by cystic ovarian follicles with a concurrent increase in estrogen production. In male dogs it is seen in testicular tumors of the (Sertoli Cells), estrogen production cells of the testicles. In both male and female dogs, the result in a bilaterally symmetrical hair loss with hyperpigmentation of the skin. Treatment is by spaying or neutering. Hair regrown and depigmentation follow.
Allergic skin disorders also cause a symmetrical hair loss and hyperpigmentation. The most common and severe allergic skin disease is Atopic Dermatitis. Atopic Dermatitis results from the genetic predisposition of dogs to develop allergies to all kinds of pollens, grasses, trees, household dust, dust mites etc and then their subsequent exposure. These are called allergens as they have the specific ability to stimulate allergy cells to secrete products that cause intense itching, chewing, gnawing, licking, etc., in animals that are genetically prone to allergies. In many cases this can also include certain foods and very often the saliva of flea bites. Below is a list of products and procedures that assist greatly in reducing the allergen exposure to your pets.
Top 10 Ways to Reduce Allergy Risk for Your Pets
1. Absolute Flea Control. Eliminate them from their skin, beds, carpets, car seats.
2. A HEPA filter for pets in the house. The HEPA filter can remove a remarkable amount of circulating allergens within the household.
3. Bedding should be cotton or other hypoallergenic material and certainly not of wool or feather composition. The bedding should be washed weekly. If the pet sleeps in bed with the owners, a plastic mattress cover should be placed over the mattress and wiped down weekly to reduce the house dust mites.
4. The hair on the paws should be clipped short and the feet wiped down with a wet house cloth when the pet comes in from outdoors. Even better would be protective shoes to prevent the allergens access to the skin. Absorption of the allergens through the skin of the feet is a major entry way of allergens into the body.
5. Frequent vacuuming of floors.
6. Weekly bathing with a soothing hypoallergenic shampoo in cool water followed by complete rinsing off of the shampoo and blotting the haircoat dry with a cotton towel.
7. Omega 3 and Omega 6 fatty acids are very helpful in reducing the inflammatory response of allergies. Nutraceuticals high in antioxidants and vitamins, particularly the B-Complex vitamins are helpful.
8. Over-the-counter antihistamines are very helpful. While Benadryl™ is the strongest, its action is only for about 3-4 hours. I currently recommend Loratidine without the decongestant at bedtime. Large dogs should get two at bedtime. If this dosage is only mildly helpful the same dose can also be given every morning as long as drowsiness or hyperactivity are not seen as side effects. Remember, check with your vets first. Always.
9. Most veterinarians including myself, advise to switch allergic dogs and cats to stainless steel or ceramic water and food bowls rather than the plastic ones.
10. Most allergic dogs will also have one or both ears affected. These should be treated with ear rinses which acidify and soothe the linings of the ear canals after they have been thoroughly cleaned out with flushes or cotton tipped cleaners. It is important to realize that the dog’s ear is not like the human ear. In the human, the ear canal goes straight into the ear to the ear drum. That is why everyone is afraid to go very deep with the cotton tipped cleaners. The dog’s ear canal goes straight down for 1-3 inches depending on the dog’s size, then curves inward and equal distance to the ear drum. As long as you go straight down the ear canal parallel to the head, you will not damage the ear drum.
Yeast Dermatitis (YD) is caused by”Malassezia" yeast that is not normally a disease causing agent unless the dog has long term uncontrolled allergic and/or bacterial skin disease, then the yeast take over the normal microbes of the skin and become pathogenic.
This causes a much thickened, hyperpigmented, oily, inflammation of the skin. The skin becomes so thickened it used to be called “elephantitis” after the thick skin of the elephant. Yeast are just the budding form of fungal organisms. This yeast dermatitis is very similar to athlete’s foot disease and "Jock itch" described so frequently in athletes and others. It responds to the same medicines if started soon enough. However once the skin becomes thickened, it usually requires prescription antifungal drugs which can be quite expensive.
There are several over-the-counter shampoos that are antifungal as well as sprays, etc. that can get it under control and keep it under control if started soon enough. However, treating and removing the primary disease of allergic or bacterial dermatitis is necessary before it can be brought under full control Most times, in my experience, allergic skin disease is the primary disease and if left untreated it can progress to a secondary bacterial disease and then to the tertiary yeast disease.
  
Hyperestrogenism Hypothyroidism Malassezia
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