Allergic Contact Dermatitis: Early Recognition and Diagnosis of Important Allergens



Allergic contact dermatitis (ACD) is an important disease with high quality of life and economic impact. Patch testing is the procedure by which identification of the cause of ACD can be elicited. Proper performance of the test, from taking an appropriate patient history to placing the correct allergens to evaluating and educating the patient, is of utmost importance. The purpose of this article is to highlight common allergens encountered in our environment, to increase awareness for this important disease, and to underscore the importance of this testing modality. An early index of suspicion can lead to appropriate testing, diagnosis, avoidance, and cure.


Allergic contact dermatitis (ACD) is a commonly seen ailment of patients visiting general medical practices and dermatology clinics. ACD was the cause of 9.2 million visits to American dermatologists in 2004, representing the third most common reason for outpatient dermatology visits ("Most prevalent skin diseases," 2005). Additionally, the caregivers in these same occupational settings, for example nurses, physician assistants, and physicians, also share a high incidence of this disease. In 2004, approximately 72 million Americans were estimated to have or had contact dermatitis allergic and irritant contact dermatitis ("Most prevalent skin diseases," 2005). In 1999, the National Research Council-Occupational Exposure Survey discerned that the cost to society of professionally treated ACD including lost work days was $1 billion annually, and this number did not include over-the-counter medications (National Occupation Research Agenda, 1999). In 2004, $1.35 billion was spent on medications and physician visits for contact dermatitis ("Most prevalent skin diseases," 2005). Even more profound about the cost of this devastating disease is that it is curable, given appropriate skilled testing, evaluation, and education.

The spectrum of contact dermatitis ranges from irritant contact dermatitis and contact urticaria to allergic contact dermatitis. Approximately 80% of the exogenous dermatides are accounted for by irritant contact dermatitis, as opposed to endogenous, such as psoriasis and atopic dermatitis. Irritant contact dermatitis represents a nonspecific response to chemical or mechanical injury corresponding to a dysfunction in the skin barrier. Detergents, water, wet work, and frequent hand washing predispose to irritant reactions because they damage the epidermal barrier. Contact urticaria (hives) represents IgE-mediated immediate type hypersensitivity. Characteristically contact urticaria presents as wheals and flares and can include severe respiratory compromise, anaphylaxis, and death. The foremost example of this would be latex hypersensitivity (Sussman & Beezhold, 1995; Wakelin & White, 1999; Yunginger, 2003). The primary focus of this article is the mechanisms and modality of allergic contact dermatitis, highlights of the most common allergens in the United States, and the use of the Thin-layer Rapid Use Epicutaneous (TRUE) test as a screening tool in private practice.

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