Appendix Home

Diet and Skin Disease

Incidence and Breed Distribution^1-3
Skin diseases are the most common problems treated by veterinarians. In many areas of the country they account for more than 50 percent of all animals presented, both normal and abnormal, to a veterinary practice. Up to 10 percent of the dermatologic problems are due to a dietary allergy. This incidence is high considering the fact that most of the skin problems result from external parasites, mostly fleas. Food allergy is more likely in certain breeds such as Labrador Retrievers, Cocker Spaniels, Collies, Springer Spaniels and Miniature Schnauzers than in others. Food allergy can appear at any age with some showing clinical signs before they are a year old. Sometimes an offending allergen is consumed for two years or longer before clinical signs appear.

Causes of Dietary-Related Skin Disease^1-3
Few studies show the cause of food-induced skin problems in dogs and cats. Veterinarians believe that dietary deficiencies are one cause because a few skin problems respond to treatment with nutrients such as zinc, vitamin A, vitamin B, vitamin E, protein or some essential fatty acids. Dietary hypersensitivity and food intolerance are more likely than a deficiency to cause skin disease. Food hypersensitivity or immune-mediated reactions develop in the same way as for digestive tract problems. Food intolerances develop when a dietary non-nutrient causes skin disease. A large number of these additives are listed in discussions on diet composition. How common are these cases. An expert states: There are no definitive reports of adverse reactions to food additives in animals. However, many clinicians have seen cats that develop pruritic skin disease when fed any commercial diet and that are asymptomatic when fed homemade diets.⁴

Histamine is released during a hypersensitivity response to food. Some foods also contain histamine as a contaminant. Chemical breakdown of the amino acid histidine forms histamine. Bacteria can cause this reaction and bacterial contamination of food can produce large amounts of histamine. Canned fish products are often high in histamine, reflecting bacterial contamination before canning. Dried and fermented foods (cheeses and meats) also contain high amounts of histamine. Some pet foods containing high histamine concentrations can cause skin problems. Some foods can promote histamine release in humans. They include egg whites, shellfish, fish, chocolate, strawberries and tomatoes. There is no evidence that these foods cause problems in dogs or cats, however.

Clinical Signs^1-3

Food allergy usually causes animals to be pruritic. The pruritus is associated with no external parasites and is nonseasonal. Many animals also show papules and some show evidence of secondary staphylococcal skin infection. In one-half of the cases the skin is markedly erythemic and shows signs of self-trauma. In longstanding cases seborrhea, hyperpigmentation and lichenification are common. Atopy, one form of allergic skin disease a dietary allergen can cause, produces pruritus of the feet, face, ears and underside of the body. Other forms of food allergy can affect any part of the body. Involvement of the ears results in otitis externa. Otitis externa is usually treated successfully with antibiotics. When otitis externa does not completely disappear or recurs after treatment stops, food allergy should be suspected as the cause.

Diagnosis of Food Allergy^1-3

The diagnosis of food allergy can be difficult to prove. There are no laboratory tests to confirm food allergy as the cause of either skin or gastrointestinal disease. Intradermal skin tests are often used to identify different allergens as the cause of skin disease. No studies have shown that skin testing for food allergens is reliable. This testing commonly produces false-positive reactions which overestimates the incidence of food allergy.

Testing for food allergy can also include radioallergosorbent tests (RAST) and enzyme-linked immunosorbent assays (ELIZA). These tests detect antibodies against specific allergens, here food allergens. No studies in dogs and cats prove any value for these tests. Many chronic skin problems are evaluated with blood tests and skin biopsies. Complete blood counts and blood chemistry panels provide little useful information for identifying food allergies or intolerances. Skin biopsies never show changes that diagnose food allergy. All biopsy changes are nonspecific, such as inflammation.

Dietary Management^1-3   

Feeding a controlled diet is the only long-term acceptable treatment for food allergies causing skin disease. A controlled diet is formulated to be balanced and free of allergens, most of which are proteins. Diets are made with ingredients most likely to be tolerated. Few studies prove that any one food is less likely than others to cause allergy.⁵ Foods believed to be best tolerated include lamb, chicken, horsemeat, venison and rabbit because they are not usually found in commercial pet foods. Lack of exposure to these foods makes it less likely they would provoke an allergic response. One of these protein sources is combined with boiled rice or potato to form the only diet for at least three weeks. Many diets for managing gastrointestinal diseases that can be used for skin diseases. Additional recipes follow. Sometimes pruritus continues for months after offending foods are removed from the diet. Current recommendations are to feed a controlled diet for 60 days before making any conclusions on unexplained and persisting pruritus.

Many commercial diets are available for treating dietary allergies. Lamb and rice are usually their primary ingredients. They may not be effective, however. Pruritus and skin disease caused by dietary allergy often disappear when dogs eat lamb and rice diets prepared by owners. Skin problems return for some when they are fed a commercially prepared diet of lamb and rice. Other than vitamins and minerals these foods contain no other nutrients. Commercial diets contain fillers, additives and preservatives that may be responsible for relapse of allergic skin disease.

An animal can be allergic to other preparations it consumes. Vitamin-mineral preparations contain meat products and additives to which an animal can be allergic. Signs of allergy often return when a vitamin-mineral tablet or powder is added to balance a controlled diet. Medications given to prevent heartworms also contain additives that can cause signs of allergy. These supplements are not given until a diagnosis of food allergy can be confirmed. Adult animals show no signs of deficiency if vitamin and mineral supplements are not given for six to eight weeks. Hypoallergenic vitamin-mineral supplements can be given when more commonly used supplements cause signs of allergy. Vitamin B₁₂ should be given by tablet several times a month or by feeding a food such as sardines that contains abundant amounts.

Rabbit and Potato Diet for Adult Dogs

1/2 cup rabbit, cooked, diced (140 grams)
3 cups potatoes boiled in skin (369 grams)
2 teaspoons vegetable (canola) oil (10 grams)
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/5 multiple vitamin-mineral tablet (made for adult humans)

provides 647 kcalories, 29.3 g protein, 17.6 g fat
supports caloric needs of 20 pound dog

Venison and Potato Diet for Adult Dogs

4 1/2 ounces (before cooking) venison, cooked (128 grams)
3 cups potatoes boiled in skin (369 grams)
2 teaspoons vegetable (canola) oil (10 grams)
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/5 multiple vitamin-mineral tablet (made for adult humans)

provides 656 kcalories, 35.7 g protein, 15.7 g fat
supports caloric needs of 20 pound dog

Rabbit and Boiled Rice Diet for Adult Dogs

1/2 cup rabbit, cooked, diced (140 grams)
2 cups cooked rice, white polished, long-grain (320 grams)
2 teaspoons vegetable (canola) oil (10 grams)
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/5 multiple vitamin-mineral tablet (made for adult humans)

provides 651 kcalories, 29.2 g protein, 18.2 g fat
supports caloric needs of 20 pound dog

Venison and Boiled Rice Diet for Adult Dogs

4 1/2 ounces (before cooking) venison, cooked (128 grams)
2 cups cooked rice, white polished, long-grain (320 grams)
2 teaspoons vegetable (canola) oil (10grams)
1/4 teaspoon salt substitute-potassium chloride
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/5 multiple vitamin-mineral tablet (made for adult humans)

provides 660 kcalories, 35.5 g protein, 16.1 g fat
supports caloric needs of 20 to 21 pound dog

Rabbit and Potato Diet for Growing Dogs

1/2 cup rabbit, cooked, diced (140 grams)
2 cups potatoes boiled in skin (246 grams)
2 teaspoons vegetable (canola) oil (10 grams)
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/5 multiple vitamin-mineral tablet (made for adult humans)

provides 511 kcalories, 26.4 g protein, 17.4 g fat
see table for a growing dog’s caloric needs

Venison and Potato Diet for Growing Dogs

4 1/2 ounces (before cooking) venison, cooked (128 grams)
2 cups potatoes boiled in skin (246 grams)
2 teaspoons vegetable (canola) oil (10 grams)
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/5 multiple vitamin-mineral tablet (made for adult humans)

provides 520 kcalories, 32.7 g protein, 15.5 g fat
see table for a growing dog’s caloric needs

Rabbit and Boiled Rice Diet for Growing Dogs

1/2 cup rabbit, cooked, diced (140 grams)
1 1/4 cups cooked rice, white polished, long-grain (200 grams)
2 teaspoons vegetable (canola) oil (10 grams)
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/5 multiple vitamin-mineral tablet (made for adult humans)

provides 497 kcalories, 26 g protein, 17.8 g fat
see table for a growing dog’s caloric needs

Venison and Rice Diet for Growing Dogs

4 1/2 ounces (before cooking) venison, cooked (128 grams)
1 1/4 cups cooked rice, white polished, long-grain (200 grams)
2 teaspoons vegetable (canola) oil (10 grams)
1/4 teaspoon salt substitute-potassium chloride
1/10 teaspoon table salt
1/2 teaspoon bone meal powder (3 grams)
1/5 multiple vitamin-mineral tablet (made for adult humans)

provides 506 kcalories, 32.3 g protein, 15.8 g fat
see table for a growing dog’s caloric needs

Skin Diseases in Cats  

Rabbit Diet for Adult or Growing Cats

3/4 cup rabbit, cooked, diced (210 grams)
1 tablespoon vegetable (canola) oil (14 grams)
1/4 teaspoon salt substitute-potassium chloride
1/4 teaspoon bone meal powder (1.5 grams)
1/10 multiple vitamin-mineral tablet (made for adult humans)

provides 352 kcalories, 31.1 g protein, 25.1 g fat
see table for a cat's or kitten's caloric needs

Venison Diet for Adult or Growing Cats

4 1/2 ounces (before cooking) venison, cooked (128 grams)
4 teaspoons vegetable (canola) oil (20 grams)
1/4 teaspoon salt substitute-potassium chloride
1/4 teaspoon bone meal powder (1.5 grams)
1/10 multiple vitamin-mineral tablet (made for adult humans)

provides 331 kcalories, 27.2 g protein, 24.6 g fat
see table for a cat's or kitten's caloric needs

Rabbit and Potato Diet for Adult Cats

1/2 cup rabbit, cooked, diced (140 grams)
3/4 cup potatoes boiled in skin (92 grams)
1 tablespoon vegetable (canola) oil (14 grams)
1/10 teaspoon table salt
1/4 teaspoon salt substitute-potassium chloride
1/4 teaspoon bone meal powder (1.5 grams)
1/10 multiple vitamin-mineral tablet (made for adult humans)

provides 378 kcalories, 23 g protein, 21.6 g fat
see table for a cat's or kitten's caloric needs

Venison and Potato Diet for Adult Cats

3 ounces (before cooking) venison, cooked (85 grams)
3/4 cups potatoes boiled in skin (92 grams)
1 tablespoon vegetable (canola) oil (14 grams)
1/10 teaspoon table salt
1/4 teaspoon salt substitute-potassium chloride
1/4 teaspoon bone meal powder (1.5 grams)
1/10 multiple vitamin-mineral tablet (made for adult humans)

provides 334 kcalories, 20.4 g protein, 17.9 g fat
see table for a cat's or kitten's caloric needs

Rabbit and Boiled Rice Diet for Adult Cats

1/2 cup rabbit, cooked, diced (140 grams)
1/2 cups cooked rice, white polished, long-grain (80 grams)
1 tablespoon vegetable (canola) oil (14 grams)
1/10 teaspoon table salt
1/4 teaspoon salt substitute-potassium chloride
1/4 teaspoon bone meal powder (1.5 grams)
1/10 multiple vitamin-mineral tablet (made for adult humans)

provides 379 kcalories, 22.8 g protein, 21.6 g fat
see table for a cat's or kitten's caloric needs