Pathomechanism of 'skin-originated' allergic diseases

The skin is outermost barrier of the body and protects us from various kinds of external stimuli. The barrier function of the skin is, however, not wholly perfect but include some 'security holes' where external antigen invades in. Further, external antigens themselves have some specific shunt pathways to breach the skin barrier. Recent studies revealed that percutaneous sensitization is a strong inducer of systemic immune responses and it is now considered that majority of food allergy is sensitized through body surfaces. Thus, to know about the fundamental structure of the skin barrier and its potential weak spots must be important for understanding the pathomechanism of 'skin-originated' allergic diseases. In this review, I overview the fundamental features of the skin barrier, and then, will discuss the pathomechanism how external antigens breach the barrier and induce subsequent systemic allergic reactions.