Nutritional Therapy in Dermatology

4. Nutritional Therapy in Dermatology

Dull Coat, Xerosis

The coat’s sheen is connected to the composition of sebum secreted by sebaceous gland secretions and stored in the hair follicles. The lipids in the composition of sebum are species and in the dog breed specific (Dunstan et al., 2000), but the production and the quality of the sebum is also influenced by food (Macdonald et al., 1983). Dryness of the skin (xerosis) is caused by decreased water content. The increased water loss through evaporation may be due to low humidity conditions of the environment or an increased transepidermal water loss. In cats, linoleic acid deficiency has been shown to be a possible cause for the latter (Macdonald et al., 1983).

Color Change of Black Coats to Reddish Brown

In some black cats, the coat color changes to a reddish brown. This color change is associated with low tyrosine plasma concentrations, has been induced in cats given a tyrosine-deficient diet, and is reversed by diets containing a high concentration of tyrosine or phenylalanine. Current dietary recommendations for dietary tyrosine and phenylalanine for kittens are below those required to support maximal melanin synthesis in black adult cats. The requirement appears to be greater than a combination of 4.5 g tyrosine plus 12 g phenylalanine/kg diet but less than 24 g phenylalanine alone/kg diet (Yu et al., 2001).

Skin Wound Healing

To maximize wound healing and to be able to formulate appropriate nutritional supplements in the pre- and post-surgery period in humans, nutritionists have studied the stimulation of re-epithelialization and of the immune system to decrease the chance of secondary wound infections. A number of oral preparations are available in human medicine, but similar products for cats are not available to the authors’ knowledge.

Protein and zinc deficiencies are associated with delayed wound healing and care should be taken to optimize protein and zinc intake in wounded animals (Robben et al., 1999).

Iron and vitamin C are involved in hydroxylation of proline, a major amino acid in the structure of collagen. Iron deficiency affects the quality of the scar tissue.

Omega-3 fatty acids have a positive effect on wound healing in dogs (Scardino et al., 1999). A vitamin E supplement helps protect PUFA’s from oxidation. Similarly, the positive role of curcumin, aloe vera and bromelaine has been shown in the canine wound healing process (Fray et al., 2004). To the authors’s knowledge, no such data exists for cats.

Feline Allergic Skin Disease

Feline atopic dermatitis is a multifactorial disease. However, in contrast to human or canine atopic dermatitis, the cat presents with a number of clinical reaction patterns (Bettenay, 2000; Rees, 2001) (Table 4). Additional common causes for these reaction patterns are flea bite hypersensitivity and adverse food reactions (see above). Nutrition may be used in several ways in these feline patients.

A diet that does not contain adequate levels of tyrosine and/or phenylalanine to permit the complete synthesis of melanin induces a coat color change in black cats. The color becomes reddish brown. (©V. Biourge).

Reduction in Inflammation with Polyunsaturated Fatty Acids

Long chain polyunsaturated fatty acids have been shown to alleviate the symptoms of miliary dermatitis (Harvey, 1993; Harvey, 1991; Lechowski et al., 1998). The fatty acid profile in plasma of affected cats was different than that of normal cats and omega-3 supplementation increased plasma concentrations of EPA and DHA and decreased dihomo-gammalinolenic acid (DGLA), corresponding to clinical improvement. A combination of fish oil (omega-3) and evening primrose oil (omega-6) had a higher response rate than fish oil alone (Harvey, 1993). Some cats with eosinophilic granuloma, another reaction pattern frequently associated with feline allergies, also respond to fatty acid supplementation (Scott et al., 2001).

Prevention or Control of Dietary Hypersensitivities

Up to 40% of cats with atopic dermatitis have concurrent adverse food reactions (Waisglass et al., 2006). Such possible dietary hypersensitivities may be addressed by either using food sources avoiding the offending protein allergens or by using a hydrolysed diet where the antigens are of such small size that an allergic reaction may be prevented in many patients.

Re-establishment of the Skin Barrier

Defects in intercellular ceramides in canine atopic epidermis have been described and presumably allow increased transepidermal water loss, increased penetration by antigens and increased adherence of staphylococci similar to what is seen in human patients with atopic dermatitis. In vitro studies (keratinocytes cultures) conducted by the Waltham Centre for Pet Nutrition have shown that some nutrients (in particular nicotinamide, pantothenic acid, histidine, inositol and choline) improve the structure and the function of the skin. Others (pyridoxine and proline) stimulate the synthesis of ceramides (Watson et al., 2006) (Figure 12).

Figure 12. Measuring the synthesis of skin lipids (From Watson, 2003).

In vivo studies have confirmed this approach. After nine weeks of supplementation with a supplement composed of nicotinamide, pantothenic acid, histidine, inositol and choline, the cutaneous water loss was significantly reduced in atopic dogs. The reduction in water loss and so xerosis can have a positive effect of reducing allergen penetration, and also limit bacterial and fungal colonization, which may cause the development of atopic dermatitis. Unfortunately, no such reports exist for the cat to the authors’ knowledge.

Miscellaneous Skin Diseases

Urticaria Pigmentosa

Essential fatty acids were reported to be helpful in the control of exacerbations of feline urticaria pigmentosa, a maculopapular eruption of the ventral trunk with a perivascular to diffuse mastocytic and eosinophilic infiltrate in the dermis (Noli et al., 2004).

Dermatosparaxis/cutaneous Asthenia

Dermatosparaxis is an inherited connective tissue disease characterized by excessive fragility and hyperextensibility of the skin. Because vitamin C is necessary in collagen synthesis, it may be useful in the treatment of feline patients with this disease. Although in contrast to dogs, two cats with dermatosparaxis treated with vitamin C did not improve (Scott et al., 2001), one of the authors has seen improvement in two cats with this syndrome treated with vitamin C.

Feline Acne

Feline acne is a disorder characterized by comedones and crusts on the chin and lips (Figure 13) and the idiopathic form is considered a disorder of follicular keratinization (Scott et al., 2001). It responds to a number of topical antimicrobial agents, but cats with recurrent feline acne have been reported to also benefit from fatty acid supplementation (Rosenkrantz, 1991).

Figure 13. Domestic short hair cat with acne. Comedones and small crusts on the ventral chin. (©R. Mueller).

Various Immune-mediated Diseases

Pemphigus foliaceus is a pustular and crusting skin disease (Figure 14) characterized by acantholysis of keratinocytes. Typically, immunosuppressive therapy with glucocorticoids or chlorambucil is recommended to treat feline pemphigus foliaceus. However, vitamin Eand fatty acid supplementation have been reported to be useful in individual patients (Scott et al., 2001). Similarly, vitamin E and essential fatty acids have been recommended as adjunctive treatment of feline discoid lupus erythematosus (Scott et al., 2001).

Figure 14. A cat with pemphigus foliaceus. Crusts on the medial pinnae. (©R. Mueller).

Prophylactic Nutrition

In feline dermatology, nutritional interventions have been almost exclusively devoted to therapeutic functions. In human dermatology, nutrition is also used preventively. The problem with preventive nutritional intervention is the identification of the patient at risk. Although most cats kept as pets are domestic short hair cats and most diseases lack clear breed predispositions in the feline, some rare dermatoses show breed predisposition such as adverse food reactions in Siamese and thus may be suited to such interventions. Prospective controlled clinical studies are needed to evaluate the benefit of such an approach.

Highly Digestible Foods

In human medicine, hydrolysates are mainly used in the prevention of adverse food reactions for high-risk children or their mothers to reduce the risk that clinical manifestations of atopy will develop (Table 10). If such an approach is useful in feline medicine remains to be elucidated.

Probiotics

In humans there is a significant difference between the intestinal flora of normal and that of atopic babies (Bjorksten et al., 2001). Similarly, it has been shown, that supplementation of pregnant and breastfeeding mothers with Lactobacillus rhamnosus significantly decreases the clinical manifestations in their children (Kalliomaki et al., 2003). In addition, supplementation with lactobacilli has improved the clinical signs of atopic children (Rosenfeldt et al., 2003).

In the cat, the addition of probiotics in food or capsules presents technical problems. In a recent study, none of the probiotic supplements tested contained all the claimed bacteria (Weese & Arroyo, 2003). However, it is possible to include probiotics in dry food and an effect on the feline immune response was observed after supplementation (Marshall-Jones et al., 2006). If these probiotics could be used for the prevention or treatment of atopic disease awaits further study.

Conclusion

Food plays a fundamental role in cutaneous homeostasis and in the treatment of many inflammatory dermatoses. The study of diet is therefore an integral part of the dermatological history. The correction of dietary imbalances (with respect to fatty acids and tyrosine in particular) is a necessary factor in good dermatological therapy.

The treatment of many dermatoses involves the use of nutrients that reinforce the skin barrier function, or modulate the immune system, either as anti-inflammatory or as immunostimulatory agents. In the future, it is likely that more emphasis will be placed on the possible use of food for prophylactic purposes. Furthermore, the exact type and dose of optimal fatty acid supplementations and probiotics will need to be determined to greatly benefit our feline patients.