2.1.1.4 Skin barrier disturbance related dermatose...
Above-mentioned mechanisms need to work together to maintain the homeostasis of skin barrier，any dysfunction of which can cause barrier damage，finally leading to the occurrence of skin diseases.In addition，genetic factors，age，inappropriate use of detergents and cosmetic products can also induce the skin barrier disturbance.The skin barriers are damaged in a variety of skin diseases，such as atopic dermatitis，irritant dermatitis，psoriasis，and staphylococcus scaled skin syndrome.The followings introduce atopic dermatitis and contact dermatitis as examples.
1.Atopic dermatitis（AD）
Epidermal barrier disturbance is closely related to the occurrence and development of AD.Filaggrin（FLG）is important in the formation of skin barriers，and the mutation of the FLG gene that encodes filaggrin is the most famous risk factor for atopic dermatitis.FLG gene mutation leads to the reduction of FLG expression，thus damages the information of skin barrier，which allows the tissue penetration of allergens，irritants and microbes.These then lead to the release of epithelial cytokines such as thymic stromal lymphopoietin（TSLP）、IL-4、IL-13 and IL-33，which play important roles in inducing type 2 immune and inflammatory.It has been proved that IL-3 and IL-4 can inhibit the epidermal barrier function，accompanied by the reduced levels of filaggrin and filaggrin degradation products，creating a permissive environment for S.aureus growth and attachment to AD skin.In AD patients，there is an exacerbation loop between the epidermal barrier and epidermal immunity，which suggests that the repair of skin barrier function is important for treating AD and preventing its development.
Studies have shown that improving the skin barrier with emollients can prevent the occurrence of AD，and in some successful studies，the uses of emollients have reduced the incidence of AD by approximately 50％.However，not all emollients application has the same effect，and the reason for which still requires further studies.(https://www.daowen.com)
2.Contact dermatitis
Contact dermatitis is usually caused by exposure to irritating or toxic substances，which disturb the skin barrier and thus cause damage to the skin's mucous membrane tissue.The main pathological mechanisms of irritancy include skin barrier damage，cytokine cascade reactions，and oxidative stress networks.The integrity of the epidermal barrier plays a key role in the human skin's response to stimuli.Different mechanisms of skin barrier impairment responses to various stimuli，but no matter what kind of stimulation，the skin barrier homeostasis will be broken.Damaged stratum corneum release more water and consequently the concentration of calcium ions in the stratum granulosum decreased，which induces lamellar body to secrete lipids，and finally lead to the occurrence of skin repair process.
In many occupation，long-term exposure to solvents，water and detergents is inevitable，which can damage the skin barrier and allow hazardous substances to enter the skin，leading to the occurrence of contact dermatitis.The use of emollients can effectively prevent contact dermatitis.