<p>Dermatitis are frequent pathologies in the consultation of small animals, being a nonspecific condition that threatens the well-being of both canines and felines and affects the dynamics of the holding family of these individuals. Within the dermatitis group, the atopic has become a difficult diagnosis and treatment condition. It is known that <em>canine atopic dermatitis (CAD)</em> is multifactorial and depends on the genetic predisposition of individuals and environmental stimuli, which may be affected by climate change. The complex immune response in canines has allowed us to understand human atopic dermatitis, becoming a medical model for research. This allergic inflammation is mediated by a type I or IV hypersensitivity response, being similar in canines and humans. Mast cells, cells with an important presence in canine skin, facilitate the recruitment of leukocytes, favour the adhesion and diapedesis of these cells, allowing the inflammatory response to be exaggerated. In the immune response cytokines, tumour necrosis factor, natural killer, among others, which facilitate communication between innate and acquired immunology, leading to the complex immune response and allowing the immune-mediated response to occur. In addition, from the individual immune response, CAD can be complicated by secondary contamination of microorganisms, which lead to their own immune responses depending on their nature. This document is intended to expose from the anatomical conformation of the skin and its immune response, the presentation of the CAD.</p>