THE ROLE OF KERATINOCYTES IN THE PATHOPHYSIOLOGY OF CONTACT DERMATITIS

Abstract

Industrialization has greatly increased exposure to chemicals, pollutants, and noxious substances, both at home and in the workplace. This trend of increasing chemical exposure continues as reliance on technology deepens. The initial barrier against these substances is the skin. In the majority of individuals, this defense is sufficient and acts without adverse effects. As exposure to chemicals becomes more widespread and frequent, the incidence of pathologic responses to this exposure in the population has increased dramatically. In 1990, the National Center for Health Statistics reported that eczematous dermatitis was one of the most common specific dermatoses encountered in the outpatient setting. 1 It is estimated that dermatitis as a result of incidental or inadvertent exposure to occupational hazards accounts for 30% of all occupational disease. More than 90% of cases described are due to irritant contact dermatitis (ICD) or allergic contact dermatitis (ACD). 85 In a study done in Denmark, hyperkeratotic hand eczema alone was estimated to affect 2.5% of Danish workers on permanent disability at a national cost of $15 million per year. 89 A direct extrapolation to the United States, based on population alone, would imply an impact of nearly $750 million per year solely for hand eczema. Thus, contact dermatitis is a disorder of significant economic dimension. This article seeks to outline the various contact dermatitides, then compare the features of ICD and ACD, and lastly to outline the immune mechanisms of contact dermatitis, with special emphasis on the role of keratinocytes.