Our objectives were to explore epidermal barrier defects in dogs with atopic dermatitis and to determine whether the defects are genetically determined or secondary to skin inflammation. First, the expression of filaggrin, corneodesmosin, and claudin1, analyzed using indirect immunofluorescence in skin biopsies collected from 32 healthy and 32 dogs with atopic dermatitis, was weaker in the atopic skin (P = .003). Second, primary keratinocytes of atopic dogs and healthy dogs were used to produce 3-dimensional reconstructed canine epidermis. The expression of the same proteins was analyzed using indirect immunofluorescence, immunoblotting, and RT-qPCR, whereas reconstructed canine epidermis morphology was investigated by transmission electron microscopy, and the barrier was investigated by functional assays. Next, inflammatory cytokines (IL-4, IL-13, IL-31, and TNFα) were added to the culture medium. The morphology, protein expression, and barrier function of the reconstructed canine epidermis were similar whether produced with keratinocytes from healthy dogs or dogs with atopy. Addition of inflammatory cytokines impaired the protein expression and epidermal barrier of the 2 types of reconstructed canine epidermis equally. To conclude, the reduced expression of epidermal barrier proteins observed in vivo was not reproduced in vitro unless cytokines were used, suggesting that it is induced by the inflammatory milieu.