Genetics and Individual Predispositions in Contact Dermatitis

Contact dermatitis cannot develop without exposure to substances in the environment. Conversely, only a part of individuals exposed to the same exogenous stimulus develop contact dermatitis, allergic or irritant. In addition, several cofactors are involved. Hence, the notion of a complex disease, with probably many genes and many environmental factors contributing to the observed phenotypes. There has been a lack of conclusive results in the study of the genetics of allergic and irritant contact dermatitis and, even more, a complete ignorance of the interplay between endogenous factors of individual susceptibility and exposure to noxious agents. In some instances, the environmental factor may override any genetic predisposition. In others, the genetic factor may prevail, with the consequence that the disease is confined to a specific subpopulation, the “noxious agent” doing no harm to the vast majority of people. The endogenous aspects of contact dermatitis and genetics and predisposition related to certain phenotypes are the focus of this chapter.