Is It Food Allergies, Atopy or What? Nutrition to the Rescue
Sherry Sanderson, BS, DVM, PhD, Dipl ACVIM, Dipl ACVN University of Georgia-College of Veterinary Medicine
Department of Veterinary Biosciences and Diagnostic Imaging
Athens, Georgia
Introduction
Nutrient Deficiencies and Skin Problems
A pet’s skin and haircoat are among some of the most visible signs of health, and owners may have concerns when their pet’s skin and haircoat are not normal. In addition to its aesthetic appeal, a healthy skin and haircoat provide other important benefits to the animal. The skin is the largest organ in the body, and it is the first line of defense against environmental insults of all kinds, such as protecting it from infectious agents and ectoparasites, as well as aiding in temperature regulation, immunoregulation and protection against water loss. The haircoat not only provides warmth, but it also protects the skin from physical trauma and injury.Good nutrition is essential for normal skin health. The skin has a relatively high requirement for protein, energy and other essential nutrients. Deficiencies in numerous essential amino acids, fatty acids, vitamins or minerals can cause problems in the skin.
Zinc Responsive Dermatosis
This condition is seen most frequently in Siberian Huskies and Alaskan Malamutes. It is a genetic defects that causes decreased zinc absorption from the intestines. Zinc is a an important co- factor in many enzymes, and zinc deficiency can present as a dermatological condition characterized by alopecia, erythema, hyperpigmentation and scaling on face.
Adverse Reactions to Food
Skin diseases may also result from adverse food reactions. Adverse reactions to food is defined as a clinically abnormal response to ingestion of a food or food additive. Adverse reactions to food can be classified as follows:
Some people inadvertently lump all adverse reactions to food as food allergies. In dogs, the most common ingredients that result in adverse food reactions include beef, chicken, and dairy In cats, the most common ingredients that result in adverse food reactions are beef, dairy, and fish. The most common manifestation of food allergies in dogs and cats is non- seasonal pruritis (ears, rears and feet for dogs and ring around the collar for cats). On the other hand, only 10 to 15% of food allergies result in gastrointestinal signs.
Therapeutic Use of Specific Nutrients to Treat Skin Diseases
Dietary Protein
The major food allergens that have been identified in people are water-soluble glycoproteins that have molecular weights ranging from 10,000 to 70,000 daltons, and are stable to treatment with heat, acid and proteases. Therefore if an animal is suspected of having a food allergy, modifying dietary protein is an important aspect of treatment. Two different approaches to modifying dietary protein can be used.
Using a novel protein source
A novel protein source is one in which the animal has not been previously exposed to. Novel protein sources vary from country to country, however, in the United States, many dog foods contain poultry, beef or lamb protein sources. Therefore, these would not be considered novel protein sources for most dogs, and therefore should be avoided in diets used in food trials. Some protein sources that would be considered novel are fish, duck, rabbit, venison, and kangaroo. It is also very important that the source of protein chosen has a very high digestibility because poorly digested proteins or partially digested proteins may actually enhance the antigenicity of the protein.
Using Protein Hydrolysate-Based Diet
Hydrolyzed protein is protein enzymatically broken down into small protein units of less than 10,000 daltons. Therefore the hydrolyzed proteins are too small to bridge IgE receptors, the mechanism by which histamine is released, causing signs of adverse food reactions. Although these diets effectively reduce histamine release, they are very expensive to manufacture, and for that reason may not be the first choice for a suspected food allergy.
Dietary Fat
It has been known for a long time that dietary fat can have a significant affect on skin and haircoat quality. Fatty acid supplements have been available for dogs and cats for years. Essential fatty acids are components of cell membrane phospholipids and precursors for a variety of compounds, including prostaglandins, leukotrienes, and other eicosanoids. Therefore essential fatty acids are essential for maintenance of epithelial tissue health and integrity. Linoleic acid, which is an omega-6 fatty acid, is an essential fatty acid for both dogs and cats. Prior to our knowledge of the effects of omega-6 fatty acids versus omega-3 fatty acids, the majority of fatty acid supplements on the market were composed of primarily omerga-6 fatty acids. Some dogs with skin problems did improve when these supplements were given.
More recently, our understanding of the differences between metabolites from omega-6 fatty acid metabolism versus metabolites from omega-3 fatty acids have led to a new way to treat inflammatory skin diseases. When omega-6 fatty acids are metabolized, they produce 2-series prostaglandins, 2-series thromboxanes, and 4-series leukotienes. These substances are proinflammatory, proaggregatory, and thrombic. However, when omega-3 fatty acids are metabolized, they produce 3-series prostaglandins, 3-series thromboxanes, and 5-series leukotienes. These substances are anti-inflammatory, antiaggregatory, and vasodilatory. Even if an animals skin disease is not due to a food allergy, supplementing the diet with omega-3 fatty acids can have beneficial effects in reducing inflammation.
The Iams Company was at the forefront of research with omega-3 fatty acids, and their therapeutic dermatological diets (Iams Veterinary Diet Response FP and Iams Veterinary Diet Response KO for dogs, and Iams Veterinary Diet Response LB for cats) were some of the first commercial diets supplemented with omega-3 fatty acids. Since this discovery, the use of omega- 3 fatty acids to treat other diseases has expanded, and the majority of commercially available dermatological diets are supplemented with omega-3 fatty acids. Many maintenance diets for dogs and cats are also supplemented with omega-3 fatty acids.
Dietary Vitamins and Minerals
A number of dermatological diseases are the result of vitamin or mineral deficiencies, or respond to supplementation of these vitamins and minerals. Examples include vitamin A, vitamin E, biotin, copper and zinc. Although diseases that respond to supplementation with these vitamins and minerals are less common than the diseases that respond to dietary protein and fat modification, nonetheless these vitamins and minerals should be kept in mind when treating certain unusual or refractory skin diseases.
What About Using OTC Products for Food Trials?
Soy Antigen Study (Willis-Mahn, et al (abstract) J Anim Phys Nutr 2011)
4 OTC dry dog foods carrying a “made with no soy” claim and 8 veterinary therapeutic dry dog foods designed for food elimination trials containing no soy in ingredient list were ELISA tested for soy. ELISA test is quantitative for soy flour protein concentrations between 2.5 and 25 ppm.
Three of 4 OTC “no soy” claiming diets were positive for soy antigen, with 2 of 4 diets containing
25 ppms soy. Four of 8 veterinary therapeutic diets had <2.5 ppm of soy protein antigens (lower detectabie limit).
Venison Antigen Study (Raditic, et al, J Anim Phys Nutr 2011)
4 OTC dry venison dog foods were tested for contamination with other protein sources not listed in ingredients (soy and beef). Three of 4 OTC “no soy” claiming diets were positive for soy antigen and one of these same diets also tested positive for beef.
Canine Atopic Dermatitis (CAD) (also called Atopy, Allergic Dermatitis and Atopic-like Dermatitis)
Recognized as a permeability barrier defect in the skin, alterations in skin microbiome and antigens, such as environmental pollens and molds. Allergens penetrate the defective skin barrier and result in inflamed skin and mast cell release of histamine and production of inflammatory cytokine.
Nutritional Management of CAD
Promote maintaining skin barrier and reducing transepidermal water loss (TEWL):
- linoleic acid and zinc supplementation have synergistic effects of reducing TEWL
- alpha-linolenic acid also helps maintain skin barrier function
- Reduce pruritis
- EPA from fish oil
- Other nutrients
- quercetin – inhibits degranulation and histamine release by mast cells
- polyphenols – reduces immediate and delayed hypersensitivity response
- Therapeutic Diets for Dogs with CAD
- Hill’s Derm Defense (egg, chicken, pork)
- Royal Canin Skin Support (fish)
