Corticosteroids for dogs & cats have been used mostly for hypersensitivity dermatosis (allergic skin reactions) to flea bite, atopy, food allergy, “hot spots” or immune mediated diseases. The corticosteroid does not cure the problem but just reduces the clinical signs of the problem. Much like putting a box over a bright light will not turn out the light but will reduce the effect of the light emitting from it. Corticosteroids are the most abused drug used by veterinarians. The correct method of administration involves alternate day therapy at the lowest dose available. Corticosteroids should not be the only treatment modality and should be used only when other less harmful methods have failed. The common procedure of giving a long acting injection of a corticosteroid can cause severe side effects as seen in the chart below. Giving the corticosteroid daily on a continuous basis causes these same side effects. We should use only the short-acting steroids, such as prednisolone, and only on an alternate day basis for long term therapy. The side effects of corticosteroid used on a continuous or long term basis, verses an alternate day therapy, are as follows:
| Clinical Sign | Treatment Modality | |||
|---|---|---|---|---|
| Daily or Long-Acting | Injection | Alternate | Daily | |
| Polydipsia (Excessive water drinking) | ++++ | +/- | ||
| Polyuria (Excessive urination) | ++++ | – | ||
| Alopecia (Hair loss) | ++ | – | ||
| Thin Skin | + | – | ||
| Liver Damage | ++ | – | ||
| Distended Abdomen | + | – | ||
| Calcinosis Cutis (Calcium deposits in the skin) | + | – | ||
| Hyperpigmentation (Excessive dark color to skin) | ++ | – | ||
| Infection | + | – | ||
| Reproductive problems | + | – | ||
| + indicates a positive occurrence | ||||
| – indicates no occurrence | ||||
The action of a corticosteroid on a pet is not entirely predictable and each pet may need to have adjustments in the dose to prevent undesirable side effects. Pets with heart disease may have special considerations prior to corticosteroid therapy to prevent the development of complications. Animals treated with corticosteroids have a tendency to develop bacterial infections of the skin, urinary, and respiratory systems.
Parasites Skin Infections in Pets
There are many parasitic skin infections in pets from exotic worms, to fleas and mange, to the
Cuterebra larva of flies. However, the most important infestation other than fleas is “MANGE”.
NOTE: Sarcoptic mange is a very common disease of dogs. It is often misdiagnosed as “allergy” and treated with corticosteroids. Studies have shown that only fifty percent of the dogs that actually have sarcoptic mange will be diagnosed based on doing twelve skin scrapings. A simple and effective test for sarcoptic mange is to rub the earflap on itself to see if the foot kicks. A positive “pinnal – pedal” reflex is a good indication that sarcoptic mange is the diagnosis. Sarcoptic mange should be treated in any animal suspected of having it because it is curable whereas allergies are not. By making a presumptive diagnosis of allergies – you are virtually condemning a dog to a life of steroids.
There are two major types of mange: Demodectic Mange and Sarcoptic Mange:
| DEMODECTIC MANGE | SARCOPTIC MANGE |
|---|---|
| Demodex canis | Sarcoptes scabiei |
| Mites are cigar or banana-shaped and live in the hair follicles. | Mites are crab-like and live in the epidermis in crusts on the outer layers of the skin. |
| Hair loss is on the face and feet primarily but may be on any area of the body. | Hair loss may be most severe on the ear margins and elbows. But the whole body can be affected. |
| The lesions are usually circular and do not itch. They may itch if they are infected. | The entire pet may itch so much that he cannot take a step without itching. |
| The mite infection is not contagious and may be hereditary. It is usually seen in purebred dogs that are highly inbred. | The mite infection is very contagious to dogs and people. |
| Stress of surgery or infection may cause it to become apparent. | The mite infection may be chronic and a pet may go undiagnosed for years and may have received steroids for “allergies” as treatment. |
| A type of white blood cell in the body is defective in that it can be turned “off” by the presence of the mite. Because the white blood cell is off, the mites can grow. | The pet with sarcoptic mange usually is a mongrel from an animal shelter but also may be a pure bred. “Scabies Incognito” is seen in pampered pets. No dermal signs just an itchy pet. Usually acquired from a grooming salon. |
| Two forms exist – localized and generalized. The localized form consists of a few spots on the body that may resolve on their own. The generalized form affects the whole body and may be fatal. | The infection is never fatal and may be diagnosed by a skin scraping. The skin scraping should be repeated in 8 to 12 places. Mites can be difficult to find. A presumptive diagnosis can be made by folding an ear on itself and rubbing it together, or by scratching the ear margin with the thumbnail. If the dog kicks the hind leg (Pinna-Pedal reflex) when this is done the pet is said to have sarcoptes until proven otherwise. |
| Skin scraping should be done for diagnosis. The skin is squeezed hard to express the mites from the follicle. Then mineral oil is applied to the skin. A dull scalpel blade or slide with oil on it is used to scrape the skin hard enough to get capillary bleeding. The hair and skin debris are collected onto a microscope slide. A coverslip is placed and the slide is examined. | Sarcoptic mange is relatively easy to kill and dipping with Mitaban®, lime sulfur, or organo-phosphate dips will be curative. Injections of ivermectin will also kill the mite. Chronic infections may occur. One injection of ivermectin has been known to eliminate infection. |
| Treatment is done with dips of Mitaban® on a weekly basis until two consecutive, weekly scrapings yield no findings. A follicle flushing shampoo such as Oxydex® is used one day prior to the dipping. | When dipping the dog, the dip should be used to clean the cage or kennel to prevent infestation of the next dog in the cage. Other equipment and utensils should be cleaned as well. |
| Home remedies are harmful and corticosteroids are very harmful and should not be given. | Home remedies are not effective. The infection on people is self-limiting and will only last for a few weeks. |
| Repeated dipping may be necessary and the mite may be impossible to eliminate due to suppression of the white blood cells. Life long therapy may be necessary. Large doses of ivermectin have recently been shown to be effective. | Sarcoptic mange is very common and is also curable. Therefore, if you suspect sarcoptic mange to be a possible diagnosis you should treat it. This will prevent a dog from being subjected to a life of steroids. |
Actions of Dermatological Agents
Benzoyl peroxide (Oxydex®, Pyoben®) containing shampoos have been used for “follicle flushing” and are keratolytic, antibacterial, antipruritic, and de-greasing.
Coal Tar— keratolytic (peeling), antipruritic (anti-itching), anti-inflammatory, at levels over 2% USP is antimitotic, keratoplastic, and vasoconstrictive.
Glycerin— moisturizing.
Lactic acid— reduces keratin formation.
Mineral/Vegetable Oil— occlusive (sealing), moisturizing.
Propylene glycol— antibacterial, moisturizing.
Salicylic acid— mildly antipruritic, bacteriostatic, and keratolytic (peeling).
Selenium— antibacterial, drying.
Sulfur— antibacterial, antifungal, antiparasitic, and drying.
Urea— moisturizing.
