ABSTRACT
Occupational skin disease is an important health burden in society and causes a signifi cant impairment in the quality of life of employees;27 where the majority of the reported cases suffer from irritant contact dermatitis of the hands.3 ICD is a nonimmunological local infl ammatory reaction characterized by erythema, edema, or corrosion following single or repeated application of a chemical substance to an identical cutaneous site.31 Studies have investigated and quantifi ed the effects of single irritant exposures, in particular sodium lauryl sulfate (SLS), which has been studied as a model irritant.4,6,13,15,17,33,38,39 However, irritation dermatitis in the workplace generally occurs with a combination of exposures to multiple irritants rather than with just a single irritant. Studies on ICD with multiple irritants have recently been studied to simulate conditions in the workplace and in consumers in a calculated and valid methodology. Various experimental designs have been used by research groups to analyze the interaction between multiple irritants in ICD, making it diffi cult to interpret and compare the data across studies in order to draw a conclusion.2,4,6,9,13-15,17,28,33,38,39,41,45
Recent studies have shown through “tandem” or sequential applications of different agents that the cutaneous response in ICD can be different compared to repeated exposures to a single irritant. The coined term tandem repeated irritation test (TRIT) has been reported as having potential in the study of repeated exposure to multiple irritants in contact dermatitis.46 The results observed in TRIT studies have shown various modifi cation of the cutaneous response compared to the response seen with exposure to single irritants. Depending on the pairs of irritants investigated, several types of cumulative irritation may result: (i) additive, a tandem response that equals the sum of the expected responses from each irritant alone; (ii) synergistic, a tandem response that is far greater than the sum of the expected response from each irritant alone; (iii) quenching, a tandem response much less than the sum of the expected response to each irritant alone. We review the development of tandem irritation studies and the possible mechanisms that may lead to the responses seen with such irritation studies. Knowledge of the trend in tandem irritation response can guide us in selecting subsequent pairs of irritants to use in future studies to elucidate the mechanism of action behind skin permeability barrier disruption in ICD.
