The stratum corneum of the skin, composed of corneocytes and intercellular lipids, plays an essential role in protecting mammals against environmental insults. Similar to atopy in humans, canine atopic dermatitis is characterized by disorganization of the lamellar lipids in the stratum corneum. This study examined the expression of canine epidermal lipids and the effect of a topically applied preparation of epidermal lipids on the abnormal subcutaneous lipid barrier in dogs with atopic dermatitis. Five atopic dogs were treated on 6 occasions at 3-day intervals with a skin lipid complex containing ceramides, free fatty acids, and cholesterol. The mixture was applied to nonlesional skin on 1 side of the dog; the symmetrically opposite nonlesional side was left untreated to serve as a control. Five nonatopic dogs were also included in the study as normal controls. One day after the final application of the skin lipid complex, punch skin biopsy samples were taken from the atopic dogs (treated and untreated sides) and from nonatopic dogs. Electron microscopy of untreated skin from atopic dogs revealed lamellar lipids that were reduced in numbers and highly disorganized. In contrast, lamellar lipids from the skin of healthy dogs were well-organized in compact sheets, filling 89.5% of the deepest intercorneocyte spaces. Treatment with the skin lipid complex resulted in an increased number of lamellar lipids in the deepest part of the stratum corneum; lamellar lipids filled 74% of the intercorneocyte spaces of the treated skin in atopic dogs, compared with only 31.8% of the spaces filled in untreated skin. The authors suggest that treatment with skin lipid complex stimulates production and secretion of endogenous stratum corneum lipids, helping to improve the epidermal barrier. Study supported by Virbac Laboratories

COMMENTARY: Recent research suggests that atopic humans have a genetic abnormality that leads to a dysfunctional skin barrier. Treating skin from the outside in is becoming more popular as an initial treatment step for these patients. This study in dogs supports the theory that topically applied ceramides, free fatty acids, and cholesterol can improve the skin barrier and improve the outcome for dogs with atopy.

Effects of a topically applied preparation of epidermal lipids on the stratum corneum barrier of atopic dogs. Piekutowska A, Pin D, Reme CA. J COMP PATHOL 138:197-203, 2008.