Allergens of New and Emerging Significance

Christen M. Mowad, MD


Dermatology Nursing. 2006;18(6):545-548. 

In This Article

Abstract and Introduction

Over 65,000 substances can cause contact dermatitis. Over 3,000 can cause allergic contact dermatitis. New chemicals are introduced into the marketplace continually. Over time, some of these chemicals emerge as allergens. Some of these new and emerging allergens are highlighted.

Patch testing is the gold standard for diagnosing allergic contact dermatitis. With so many chemicals available that can cause irritant contact dermatitis or allergic contact dermatitis, history and physical exam alone are not sufficient for diagnosis. Patch testing is necessary for identifying causative allergens responsible for a given dermatitis. Furthermore, new allergens are continually introduced into the marketplace and some of these chemicals emerge as allergens. Patch testing is needed to diagnose sensitivity to these allergens. Through patch testing, allergens can be identified and dermatitis due to these allergens can be resolved. Without patch testing, allergic contact dermatitis may go undetected, resulting in increased patient costs, increased morbidity, and delay in accurate diagnosis and treatment with a corresponding decrease in quality of life (Rajajopalan et al., 1998).

The number of physicians performing patch testing in the office setting has increased since the introduction of the TRUE Test® (Warshaw & Nelson, 2002). This prepackaged testing system with its ease of application has simplified the patch test procedure and more physicians are patch testing as a result. Although it has increased patch testing for allergic contact dermatitis, allergens can be missed using this testing technique. The TRUE Test can evaluate 28% of clinically relevant positive reactions, but it completely misses relevant allergens in 22.4% of patients (Saripalli, Achen, & Belsito, 2003). Therefore its usefulness is limited. As a result, physicians must have a high level of suspicion for the possibility of allergic contact dermatitis and keep in mind the numerous allergens that can be causative. Expanded patch testing beyond the TRUE Test should be considered and pursued when appropriate.

Many supplemental allergens are available from companies outside the United States. For example, Dormer Laboratories ( and Omniderm Pharma Canada Inc. ( distribute supplemental allergen tests and allergen series. These allergens include expanded series for routine testing as well as specialized series to be used when the history suggests, such as nail trays, dental series, plastics and glues or plant series, cosmetic series, or shoe series. These allergens series may not be appropriate for routine testing but can be very useful in certain situations. These supplemental allergens come in prefilled multi-use syringes and are poured into Finn Chambers. They are then taped to the back, kept dry, and left in place for 48 hours. At that point an initial reading is performed. The patients are asked to keep the back dry and return for a second reading 3 days to 1 week after the initial application of patches. Although the TRUE test is a reasonable starting point, supplemental allergens can provide a more thorough and complete evaluation.


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