Chemistry of contact allergens and irritants

Understanding the nature and causes of contact dermatitis is as much a problem of chemistry as it is of biology. Many of the characteristics of an individual's reaction to a particular chemical, whether it be an irritant or allergen or both, depend very much on that person. From a more general perspective, however, the ability of a chemical to irritate and/or sensitize is a primary function of its chemical properties. The human biological system simply responds to the nature of the chemical perturbation it perceives; thus within the human population there is normal distribution in terms of the intensity of a reaction to a defined stimulus. This article reviews the present state of knowledge regarding the relationships between the ability of a chemical to cause contact dermatitis and its physicochemical properties, with close attention paid to how this knowledge may be used in a predictive sense to assist in risk assessment.