The skin has multiple functions, and one of the most important is the barrier. It prevents water loss (inside-outside barrier) and protects the body from the environment (outside-inside barrier). The barrier function is depending on the stratum corneum (SC), and the ceramides of this SC are a very important component. It has been suggested that atopic dermatitis (AD) is associated with a defective barrier function. One study¹ assessed barrier function with transepidermal water loss (TEWL, the volume of water that passes from inside to outside the body through the upper epidermal layers) and they found a higher TEWL in dogs with AD vs. controls. In the same study, treated AD had lower TEWL compared to non treated, suggesting that skin barrier function is susceptible to be improved by medical treatment and is associated with a good clinical response.

Nutrition is important to ensure a healthy skin barrier.² It is not fully known whether nutritional modification can improve the skin barrier function in dogs and cats with disease, although there is some promising research in this area.

Nutrient Deficiencies and Skin Disease

The skin is the largest organ in the body with a high turnover rate, thus, several nutrient deficiencies can result in skin problems,³ including protein and some amino acids, omega-6 essential fatty acids, trace elements, water soluble vitamins, and lipid soluble vitamins. These are all unlikely in patients with adequate digestive and absorptive processes that are fed complete and balanced diets. Unbalanced home cooked diets can result in all of these deficiencies.

Important Nutrients for Skin Function

Essential Fatty Acids

Essential fatty acids (EFA) are fatty acids from the omega-6 and -3 families. Linoleic acid is an omega-6 EFA that is incorporated in the ceramides of the SC⁴ and whose deficiency results in dry, coarse skin. High fat diets or vegetable oil supplements like corn oil can improve hair coats quality in dogs. Omega-6 EFA are more potent than omega-3s to promote skin barrier function.

Oral supplementation with EFA (especially with linoleic acid) suggests improvement of ceramide synthesis in dogs, although the studies are still scarce and more data is needed to confirm its effect and decide on an appropriate route, dose and composition of the treatment.⁵

B Vitamins and Others

One study found a positive effect on TEWL of healthy dogs with a diet supplemented with pantothenic acid, niacin, choline, inositol, and histidine. These nutrients showed in vitro stimulation of ceramide synthesis in canine keratinocytes.⁶ One small study with dogs fed this combination of nutrients suggested that it could help reduce itch in Labrador puppies when fed for one year.⁷ However, there is very little data on the effects of supplementing these nutrients separately and no data on how does this combination work to improve skin barrier function.

Fat Soluble Vitamins

Vitamin A is very important for all epithelia and its deficiency results in altered skin barrier function but there is no data to support its supplementation to help skin barrier. Vitamin E, an antioxidant, is important to protect fatty acids (including those in the SC) from damage. One study found dogs with atopy had lower plasma vitamin E and that supplementation (8.1 IU/kg q 24 hours for 8 weeks) improved the subjective pruritus score. However, it is unknown if this relates to improvement of skin barrier.

References

1.  Cornegliani L, Vercelli A, Sala E, et al. Transepidermal water loss in healthy and atopic dogs, treated and untreated: a comparative preliminary study. Vet Derm. 2011;23:41–44.

2.  Hensel P. Nutrition and skin diseases in veterinary medicine. Clin Dermatol. 2010;28:686–693.

3.  National Research Council. Nutrient Requirements of Dogs and Cats. Washington DC: The National Academies Press; 2006.

4.  Reiter LV, Torres SM, Wertz PW. Characterization and quantification of ceramides in the nonlesional skin of canine patients with atopic dermatitis compared with controls. Vet Dermatol. 2009;20:260–266.

5.  Popa I, Pin D, Remoué N, et al. Analysis of epidermal lipids in normal and atopic dogs, before and after administration of an oral omega-6/omega-3 fatty acid feed supplement. A pilot study. Vet Res Commun. 2011;35:501–509.

6.  Watson AL, Fray TR, Bailey J, et al. Dietary constituents are able to play a beneficial role in canine epidermal barrier function. Exp Dermatol. 2006;15:74–81.

7.  van Beeck FL, Watson A, Bos M, Biourge V, Willemse T. The effect of long-term feeding of skin barrier-fortified diets on the owner-assessed incidence of atopic dermatitis symptoms in Labrador retrievers. J Nutr Sci. 2015;4:e5.