The skin barrier is a very important element of the body as it plays crucial roles in the immune surveillance and epidermal homeostasis, and in stopping entrance of microorganisms and allergens. The capacity of the skin to protect the body relies on its structure that includes different layers of cells containing components such proteins and lipids organized in such a way that they provide a tight and strong structure to the skin. Due to various factors, impairments of the structural integrity of the skin occur and compromise its barrier functions provoking thereby immune responses that lead to inflammatory reactions responsible for skin diseases such as dermatitis. According to the causative agent, the location and the symptoms, different types of dermatitis can be identified. These include for example allergic contact dermatitis, atopic dermatitis known as eczema, seborrheic dermatitis and nummular dermatitis. Common symptoms are associated with dry and itchy skin accompanied by the occurrence of blisters. Both genetics and environmental factors play a role in the occurrence of dermatitis. The genetic factors include mutations in genes coding for important skin proteins such as filaggrin responsible for different functions mainly in relation to water retention. Environmental factors can be associated with allergens, detergent, surfactant, excessive washing and exfoliation, and inappropriate diet. This research paper provides an overview of the occurrence of dermatitis in relation to defects in the skin barrier function. Different types of dermatitis, the normal skin structure components, and its associated functions are discussed. Moreover, the basis for structural defects in the skin in relation to mainly atopic dermatitis, with an emphasis on filaggrin and its genetic underpinnings are reviewed. Aspects of the innate and adaptive immunity, including the role of anti-microbial peptides and proteases are also depicted.