Utility of a standard allergen series alone in the evaluation of allergic contact dermatitis: a retrospective study of 732 patients

Analysis of patch testing results in patients with contact dermatitis in Istanbul, Turkey, from 2012 to 2022

BACKGROUND

Allergens responsible for allergic contact dermatitis (ACD) differ between populations. They can even change over the years with the effect of environmental factors.

AIMS

To evaluate the results of patch testing performed in our center.

METHODS

In this study, the thin-layer rapid-use epicutaneous (T.R.U.E.) test results of patients with a diagnosis of ACD between 2012 and 2022 were retrospectively evaluated.

RESULTS

In 431 (42.5%) of the total 1012 patients, a positive reaction to at least one allergen was detected in the patch test. Allergen positivity was most detected for nickel sulphate (16.8%), gold sodium thiosulfate (GST) (6.9%), thimerosal (4.2%), fragrance mix (3.4%), carba mix (3.2%), and cobalt dichloride (2.9%). Nickel sulfate and GST sensitivity was found to be significantly higher in women, fragrance mix sensitivity in men, thimerosal sensitivity in individuals aged under 40 years, colophony and balsam of Peru sensitivity in head and neck dermatitis, and carba mix and thiuram mix sensitivity in atopic individuals.

CONCLUSIONS

This study presents comprehensive data from Turkey concerning the sensitivity frequencies for allergens included in the T.R.U.E. test.

The Added Value of Patch Testing Beyond the Baseline Tray

BACKGROUND

The patch test is the standard for diagnosing allergic contact dermatitis. Standardized trays allow the examination of the most prevalent allergens, whereas customized trays are more appropriate for addressing specific allergens and require expertise. They are therefore usually performed in specialized clinics.

METHODS

We assessed the results of 4355 patch tests performed between 2012 and 2020 in a contact dermatitis clinic located in a large tertiary medical center. All patients were tested using the European baseline series and additional trays as clinically indicated. We assessed the frequency of relevant positive reactions outside the European baseline series. We then examined the added value and number of tests (NNTs) that need to be performed to elicit one relevant positive reaction per tray and common allergens.

RESULTS

Nine hundred fifty-four patients (21.9%) had 1 or more positive relevant reactions; 43.3% tested positive for an allergen outside the European baseline series (OEBS). The acrylate and fragrance trays were highly represented among the positive and relevant reactions OEBS with NNTs of 4.4 and 6.8, respectively. 2-Hydroxyethyl methacrylate is the most prevalent allergen OEBS and is considered a marker for acrylate sensitivity with a high rate of cross-reactions and concordance rate of 85%, justifying its addition to the EBS in 2018. Other highly represented allergens include chloramphenicol, 2-hydroxyethyl acrylate, and Amerchol L-101, a lanolin derivative. The cosmetics and textile trays, although often tested, have relatively low added values of 3.7% and 2.3%, respectively. Surprisingly, the cutaneous adverse drug reaction series tray (CAD-1000) yielded no positive reactions, whereas testing the patients' medication yielded positive results in 10.9% of the cases.

CONCLUSIONS

Expanded patch testing is crucial to accurately diagnose allergic contact dermatitis and almost doubles the number of patients with relevant positive reactions. Acrylate sensitivity is an emerging epidemic with a high positive reaction rate and low NNT, as is sensitivity to the allergens in the fragrance tray. 2-Hydroxyethyl methacrylate is a reliable marker for acrylate sensitivity with a concordance rate of 85%. Chloramphenicol is a common culprit and should be added to the standard tray in countries with a high usage rate. A low NNT was also observed when testing the patients' own cosmetics and medications; this should, therefore, be encouraged. The textile tray yielded a relatively high NNT; however, it should be performed when clinically indicated in the absence of a reliable marker in the EBS.

Importance of Supplemental Patch Testing Beyond a Screening Series for Patients With Dermatitis: The North American Contact Dermatitis Group Experience

IMPORTANCE

Patch test screening series for patients with dermatitis are limited and may miss clinically relevant contact allergens.

OBJECTIVE

To characterize individuals with dermatitis who showed clinically relevant patch test findings to supplemental (nonscreening) allergens or substances.

DESIGN, SETTING, AND PARTICIPANTS

A 17-year, retrospective cross-sectional analysis (January 1, 2001, to December 31, 2018) of North American Contact Dermatitis Group (NACDG) data from multiple centers in North America was conducted. A total of 43 417 patients with dermatitis underwent patch testing to the NACDG screening series in a standardized manner with 65 to 70 allergens and supplemental allergens as clinically indicated. Patients with 1 or more clinically relevant reactions to a supplemental (nonscreening) allergen/substance were analyzed between November 18, 2020, and March 12, 2021.

MAIN OUTCOMES AND MEASURES

The main outcomes were to assess the number of patients with clinically relevant reactions to supplemental (nonscreening) allergens and compare characteristics (including demographic characteristics and occupations) between patients with a clinically relevant patch test reaction to 1 or more supplemental allergens or substances (supplement-positive) and those without a reaction (supplement-negative) using odds ratios (ORs) and 95% CIs. Secondary outcomes included sources of allergic contact dermatitis and, for occupationally related cases, specific occupations and industries.

RESULTS

Of 43 417 patients included in the study who underwent patch testing to the NACDG screening series (65-70 allergens), 9507 individuals (21.9%) had currently relevant reactions to 1 or more supplemental allergens or substances. Of these, 6608 were women (69.5%) and the mean (SD) age was 47.2 (0.54) years. Compared with patients who had supplement-negative results, patients with supplement-positive findings were significantly less likely to be male (OR, 0.90; 95% CI, 0.85-0.94; P < .001) and/or have atopic dermatitis (OR, 0.89; 95% CI, 0.84-0.93; P < .001). Common primary sites of dermatitis in 9499 patients with supplement-positive findings included the face (2856 [30.1%]), hands (2029 [21.4%]), and scattered/generalized distribution (1645 [17.3%]). Frequent sources of supplemental allergens in 9235 patients included personal care products (4746 [51.4%]) and clothing/wearing apparel (1674 [18.1%]). Of 9362 patients with available data, supplemental allergens/substances were occupationally related in 1580 (16.9%); of those with identified occupations, 25.1% (384 of 1529) were precision production, craft, or repair workers. Of 9507 patients with supplement-positive findings, 2447 (25.7%) had no currently relevant reactions to NACDG screening allergens.

CONCLUSIONS AND RELEVANCE

This cross-sectional study found that 21.9% of patients who underwent patch testing to an allergen screening series of 65 to 70 allergens had at least 1 relevant reaction to supplemental allergens/substances. Of these, one-quarter reacted only to a supplemental allergen/substance. Screening series include common, important allergens, but these findings suggest that the addition of specialty allergens and personal or work products is critical for the successful diagnosis and management of allergic contact dermatitis.

Patch test informed consent form: position statement by European Academy of Dermatology and Venereology Task Force on Contact Dermatitis

BACKGROUND

To our knowledge, an international consensus is lacking regarding the development of an adequate informed consent form for a patch test (PT) and the information that should be included in such document.

OBJECTIVES

The aim of the study was to reach a consensus on the specific points that need to be addressed in a PT consent form.

METHODS

A Delphi survey, comprising 2 rounds and 1 final discussion, was used to gather and analyse data, which was conducted over the Internet. Each statement that reached a consensus with the respondents (9 expert dermatologists from Europe) was defined as a median consensus score (MED) of ≥7 and agreement among panelists as an interquartile range (IQR) of ≤3. All study participants were members of the EADV task force on contact dermatitis.

RESULTS

The expert panel addressed several topics that should be included in an informed consent form for a PT: introduction, preparation for PT, testing procedure, allowed activities, adverse events and additional authorizations.

CONCLUSIONS

Our results assess recommendations regarding points to be contained in an informed consent form for a PR. Future actions towards standardization and harmonization of this specific consent form are needed.

Patch Testing Pearls

Dermatitis is one of the most common illnesses encountered by healthcare providers and the causes are numerous. Contact dermatitis is the form of dermatitis resulting from contact with the environment, and it may be either irritant or allergic in nature. Patch testing has been the gold standard for diagnosis of allergic contact dermatitis since its formal description over 100 years ago by Jadassohn. While this diagnostic tool may seem simple to us today, there are numerous potential points for error that the practitioner must keep in mind. Patient selection, technique of patch test placement, allergen selection, patch test reading and interpretation, and patient management all must be considered. To simply apply a given set of test allergens indiscriminately and not be prepared to interpret the results accurately with patient education and management in mind would be a great failure. Conversely, with experience and the proper knowledge base some of the most complex dermatitis questions can be answered.

Patch Test Negative Generalized Dermatitis

Allergic contact dermatitis is a common condition in dermatology. Patch testing is the criterion standard for diagnosis. However, dermatitis is not always caused by an allergen, and patch testing does not identify a culprit in every patient. Generalized dermatitis, defined as eczematous dermatitis affecting greater than 3 body sites, is often encountered in dermatology practice, especially patch test referral centers. Management for patients with generalized dermatitis who are patch test negative is challenging. The purpose of this article is to outline an approach to this challenging scenario and summarize the paucity of existing literature on patch test negative generalized dermatitis.

International survey on skin patch test procedures, attitudes and interpretation

BACKGROUND

Skin patch test is the gold standard method in diagnosing contact allergy. Although used for more than 100 years, the patch test procedure is performed with variability around the world. A number of factors can influence the test results, namely the quality of reagents used, the timing of the application, the patch test series (allergens/haptens) that have been used for testing, the appropriate interpretation of the skin reactions or the evaluation of the patient's benefit.

METHODS

We performed an Internet -based survey with 38 questions covering the educational background of respondents, patch test methods and interpretation. The questionnaire was distributed among all representatives of national member societies of the World Allergy Organization (WAO), and the WAO Junior Members Group.

RESULTS

One hundred sixty-nine completed surveys were received from 47 countries. The majority of participants had more than 5 years of clinical practice (61 %) and routinely carried out patch tests (70 %). Both allergists and dermatologists were responsible for carrying out the patch tests. We could observe the use of many different guidelines regardless the geographical distribution. The use of home-made preparations was indicated by 47 % of participants and 73 % of the respondents performed 2 or 3 readings. Most of the responders indicated having patients with adverse reactions, including erythroderma (12 %); however, only 30 % of members completed a consent form before conducting the patch test.

DISCUSSION

The heterogeneity of patch test practices may be influenced by the level of awareness of clinical guidelines, different training backgrounds, accessibility to various types of devices, the patch test series (allergens/haptens) used for testing, type of clinical practice (public or private practice, clinical or research-based institution), infrastructure availability, financial/commercial implications and regulations among others.

CONCLUSION

There is a lack of a worldwide homogeneity of patch test procedures, and this raises concerns about the need for standardization and harmonization of this important diagnostic procedure.

Patch testing: pitfalls and performance

PURPOSE OF REVIEW

Contact dermatitis is a common disease process that includes allergic and irritant contact dermatitis. The gold standard for diagnosing allergic contact dermatitis, a type IV delayed hypersensitivity reaction, is patch testing. Patch testing is not a difficult procedure, however, there are several critical components that determine the success of the test: having an appropriate level of suspicion for the diagnosis of allergic contact dermatitis, an adequate threshold for patch testing, the necessary experience to properly interpret the results and to determine their relevance, and the ability to thoroughly educate the patient about the condition.

RECENT FINDINGS

Research shows that patch testing practices differ among individuals and specialties. The level of patch testing education, interest in, and experience with, the procedure can affect the results of the test. Some of these practice differences and how they affect the outcome of patch testing are highlighted.

SUMMARY

Physicians' knowledge and experience with patch testing, their level of interest and access to allergens will determine the performance of this test, the reliability of the results and the benefits gained from this procedure.

Contact Dermatitis and Workforce Economics

The roots of education in patch testing begin with Jadassohn and have been passed down through generations of dermatologists through didactic teachings and mentoring. Currently, we are faced with workforce economics tipping the balance of dermatology toward cosmetic and surgical practices. This imbalance is easily found in the subspecialty of contact dermatitis, where the current demand for patch test services is on the rise and the number of new dermatology-based patch test providers cannot keep up with the current demand. Steps are being made to remedy this discrepancy through societies and fellowships, yet the question remains: were the steps in time and were they big enough?

Patch testing: a retrospective analysis of 103 patients with emphasis on practical aspects for the clinician

BACKGROUND

Allergic contact dermatitis is a common dermatologic disorder caused by small chemical molecules that can penetrate the skin barrier. Thousands of chemicals capable of inducing allergic contact dermatitis have been identified. To cure allergic contact dermatitis, the allergen should be identified and eliminated from the environment of the patient. Patch testing, utilizing a variety of standard panels of the most frequent allergens, is used to identify the allergen in question. Patch testing is still the gold standard tool used to identify one or more substances that may contribute to the etiology of allergic contact dermatitis.

OBJECTIVE

To determine the frequency of patch test positivity and to identify the most common allergens in patients with suspected allergic contact dermatitis.

METHODS

A retrospective analysis of files of 103 patients who have been clinically diagnosed to have allergic contact dermatitis and have been patch tested using a standard technique with a Northern American Contact Dermatitis Group series.

RESULTS

Sixty-two patients (60.2%) showed positive reactions to one or more substance. The most common allergens were nickel sulfate, fragrance mix, and neomycin sulfate. There was an increased frequency of positive reactions to fragrance mix and a significant decrease of frequency of thimerosal positive reactions.

CONCLUSIONS

Increased awareness of allergens and their potential sources may help to limit the usage of these chemicals in manufacturing consumer products. This may have contributed to decreased prevalence rates of certain allergens such as thimerosal and paraphenylenediamine.

Prevalence and relevance of contact dermatitis allergens: a meta-analysis of 15 years of published T.R.U.E. test data

BACKGROUND

The patch test procedure is frequently employed to help determine or confirm the cause of allergic contact dermatitis (ACD). The T.R.U.E. Test has become a global standard and is the commercially available patch test system currently used within the United States. Although many studies report T.R.U.E. Test data, none has measured the overall prevalence and relevance of reactions to the allergens tested by the T.R.U.E. Test. Our objective is to describe the prevalence and relevance of contact dermatitis allergens as tested by the T.R.U.E. Test.

METHODS

We conducted a search of the MEDLINE database from 1966 to June 2000 for all publications on the use of the T.R.U.E. Test in the clinical evaluation of ACD in human subjects. Inclusion and exclusion criteria were applied. For each study, we identified and recorded the number of subjects tested, the number of patients with positive reactions, and the number with relevant reactions. Data were analyzed using the SAS system (Cary, NC).

RESULTS

Ours is the first study to compile the entire corpus of published T.R.U.E. Test data and to examine these data using meta-analytic techniques. The meta-analysis shows that nickel (14.7% of tested patients), thimerosal (5.0%), cobalt (4.8%), fragrance mix (3.4%), and balsam of Peru (3.0%) are the most prevalent allergens. The 5 least prevalent allergens are paraben mix (0.5%), black rubber mix (0.6%), quaternium-15 (0.6%), quinoline mix (0.7%), and caine mix (0.7%). By contrast, North American Contact Dermatitis Data Group (NACDG) data show that the 5 most prevalent allergens are nickel (14.3%), fragrance mix (14%), neomycin (11.6%), balsam of Peru (10.4%), and thimerosal (10.4%). NACDG data indicate that the prevalence of allergy to cobalt is 9.2%. In order to assess the clinical importance of T.R.U.E. Test allergens, we employ the Significance-Prevalence Index Number (SPIN). Based on SPIN, the most clinically important allergens tested by the T.R.U.E. Test are nickel (SPIN=894), cobalt (266), fragrance mix (158), colophony (141), and thiuram mix (138).

CONCLUSIONS

Our results identify the prevalence of common contact dermatitis allergens as tested by the T.R.U.E. Test and are in general agreement with previously published reports using other patch test methods. Over 3700 allergens have been identified as causing ACD, of which the T.R.U.E. Test tests only 23. Thus, the T.R.U.E. Test is a screening test at best. Comparison with NACDG data suggests that clinically important allergens may be missed by the T.R.U.E. Test.

Clues to an accurate diagnosis of contact dermatitis

An accurate diagnosis of allergic contact dermatitis can be achieved by a combination of historical, morphologic, and diagnostic steps. Clues in the history and physical examination can point to an irritant as the source of contact dermatitis. While irritants and allergens share many common features both immunologically and clinically, there are grounds for the distinction. Knowledge of occupational factors is necessary to assess the source of contact dermatitis. A common pitfall is the failure to appreciate the role of endogenous factors in the clinical presentation and overall care of the dermatitis patient. A comprehensive assessment of the patient's environment will lead to appropriate patch tests being applied and a correct diagnosis being reached.

Patch testing with a standard allergen ("screening") tray: rewards and risks

The TRUE Test panels, which are the only patch testing devices approved by the Food and Drug Administration in the US, consist of 24 patches, one of which is a negative control. The remaining 23 patches contain 42 unique allergens and four complex mixtures. Although these panels contain approximately 1.4% of the > 3700 known allergens, they perform robustly in detecting allergic contact dermatitis (ACD). Twenty-eight percent of patients are fully evaluated by application of TRUE Test((R)). The present paper reviews the appropriate use of the TRUE Test panels. The need to determine relevance of any positive reaction is stressed. The common causes of false-positive and false-negative reactions are outlined. Those product types where the TRUE Test panels detect the majority of relevant allergic reactions are reviewed, as are the other sources of exposure to the allergens on these panels. The impact of ACD on quality of life is significant. Only by patch testing can the diagnosis be made.

The detection of clinically relevant contact allergens using a standard screening tray of twenty-three allergens

BACKGROUND

The current standard tool for diagnosing allergic contact dermatitis (ACD) in the United States is the T.R.U.E. test panels, which consist of 23 allergens. Previous studies have raised concern regarding the adequacy of these panels in fully assessing patients with possible ACD.

OBJECTIVE

We sought to examine the use of the T.R.U.E. test allergens as the primary diagnostic method for detecting ACD.

METHODS

A retrospective analysis of all patients with possible ACD who presented to the University of Kansas' Section on Occupational and Contact Dermatitis in Kansas City, Kansas, and subsequently underwent patch testing from January 1, 1995, to December 31, 2001. Patients with positive allergic reactions were stratified into 3 groups: (1) reactions only to allergens on the T.R.U.E. test; (2) reactions only to allergens not present on the T.R.U.E. test; and (3) reactions to allergens on the T.R.U.E. test and additional allergens. These 3 groups were further analyzed to assess clinical relevance.

RESULTS

Of the 898 patients who were patch tested, 616 (68.6%) had at least 1 positive allergic reaction. Among these 616 patients, 25.5% would have been fully evaluated using the T.R.U.E. test allergens only. Of the remaining patients, 22.4% would not have had any of their allergens detected and 52.1% would have only been partially evaluated had only the T.R.U.E. test allergens been used. Similar percentages were observed when only patients with clinically relevant reactions were included.

CONCLUSIONS

In our study, the current T.R.U.E. test series of 23 allergens would have completely identified all allergens in only 25.5% of patients and clinically relevant allergens in 28% of patients. Expanding the number of allergens used according to a patient's environment and history will lead to improved outcome in the treatment and prevention of ACD.

Evaluation of the Skin and Cancer Foundation standard series in the diagnosis of allergic contact dermatitis

The use of a standard series of 37 allergens was evaluated in a retrospective study of 817 consecutive patients seen between April 1988 and January 1993 at the Skin and Cancer Foundation, Melbourne, Australia. Of the 316 patients with clinically relevant patch test results, 134 (42%) reacted to an allergen in the standard series alone, while an additional 122 (39%) had reactions to allergens in both the standard and supplementary series. The remaining 60 (19%) patients reacted only to allergens in the supplementary series. These data suggest that the use of our standard series alone will detect about 80% of allergic contact dermatitis cases, but that many of these may be insufficiently evaluated. Use of supplementary allergen testing in a specialised clinic is recommended for patients who may have allergic contact dermatitis.

The true value of the TRUE Test for allergic contact dermatitis

The development of the thin layer rapid use epicutaneous (TRUE) Test is a history of cooperation between scientists from academia and industry covering several disciplines: medicine, pharmaceutical chemistry, pharmacology, and statistics. The TRUE Test is today a patch test system with documented stability and allergen content. Allergens are incorporated in a dried-in-gel vehicle, which is coated onto a polyester backing to form a patch. Applied to the skin, the allergens are released when the gel becomes moisturized by transepidermal water. This may seem to be a simple technique, but its development required laborious research and solutions to stability and dosage problems. The test has been clinically standardized with serial dilution tests on sensitized patients and validated in comparative multicenter tests. The test is a significant step towards higher reliability of patch testing. Fifteen years of experience and critical investigations are discussed in this article, as are possible improvements such as expansion of the test with new allergens.

The diagnostic evaluation, treatment, and prevention of allergic contact dermatitis in the new millennium

Identifying the etiology of allergic contact dermatitis is a rewarding yet challenging endeavor. Not all allergic contact reactions are eczematous in appearance. The most reliable clinical clue to the allergic nature of the dermatitis is its geographic distribution. Once a list of culprit allergens has been identified by patch testing, the practitioner must identify the relevant allergen(s) and counsel the patient in avoidance. For most individuals, allergen avoidance results in resolution of the dermatitis; however, some patients will require continuing symptomatic therapy despite avoidance. For those patients unable to avoid known allergens, immunosuppressant therapies (including phototherapy) or barriers can be beneficial. Currently, hyposensitization is not a viable alternative for the treatment of allergic contact dermatitis.

Thoughts on sensitizers in a standard patch test series. The European Society of Contact Dermatitis

Patch testing is the predominant method of establishing contact allergy. The present patch test technique is the result of a continuous process of development and improvement since its first application in the late 19th century. The perfect patch test should give no false-positive and no false-negative reactions. The ideal patch test should also cause as few adverse reactions as possible, particularly no patch test sensitization. Even though the history and examination of a patient with suspected allergic contact dermatitis will give clues to possible sensitizers, it is not sufficient to patch test only with initially suspected sensitizers; unsuspected sensitizers used for patch testing frequently turn out to be the real cause of the dermatitis. Fortunately, a small number of substances are considered to account for the majority of delayed hypersensitivity reactions. Therefore, generally 20-25 test preparations consisting of chemically defined compounds, mixes of allergens, and natural and synthetic compounds, are grouped into a standard test series. The requirements to be fulfilled by a sensitizer in a standard patch test series are discussed in this article. A procedure of investigations is proposed before a sensitizer is included in a standard series.

North American Contact Dermatitis Group patch test results for the detection of delayed-type hypersensitivity to topical allergens

BACKGROUND

Allergic contact dermatitis is a significant cause of cutaneous disease affecting many individuals. Patch testing, when used properly, often provides support for the diagnosis of allergic contact dermatitis.

OBJECTIVE

This article reports patch testing results from July 1, 1994, to June 30, 1996, by the North American Contact Dermatitis Group (NACDG).

METHODS

Patients evaluated in our patch test clinics were tested with the same screening series of allergens by the use of a standardized patch testing technique. The data from these patients were recorded on a standard computer entry form and analyzed.

RESULTS

Forty-nine allergens were tested on 3120 patients. Budesonide was added to the series in July 1995 and tested on 1678 patients. Of these patients, 66.5% had positive allergic patch test reactions, and 57% had at least one allergic reaction that was felt to be clinically relevant to the present or past dermatitis. The 20 screening allergens commercially available to United States dermatologists in the Allergen Patch Test Kit, accounted for only 54.1% of the patients with positive allergic reactions. The additional 30 allergens on the NACDG screening series accounted for 47% of patients with positive allergic reactions. Had the Allergen Patch Test Kit alone been used, 12.4% of all patients tested may have had their disease misclassified as a nonallergic disorder, and an additional 34.4% of all tested patients would not have had their allergies fully defined. Among those patients with positive responses to the supplemental allergens, 81% of the responses were of present or past relevance. The 12 most frequent contact allergens were nickel sulfate, fragrance mix, thimerosal, quaternium-15, neomycin sulfate, formaldehyde, bacitracin, thiuram mix, balsam of Peru, cobalt chloride, para-phenylenediamine, and carba mix. The present relevance varied with the specific allergen from 10.7% (thimerosal) to 85.7% (quaternium-15). Among newer allergens, methyldibromoglutaronitrile/phenoxyethanol (cosmetic preservative) caused positive allergic reactions in 2% of the patients; tixocortol-21-pivalate and budesonide (corticosteroids), in 2.0% and 1.1% of the patients, respectively; and ethylene urea/melamine formaldehyde mix (textile resin), in 5% of the patients.

CONCLUSION

The usefulness of patch testing is enhanced with the number of allergens tested, because allergens not found on the commercially available screening series in the United States frequently give relevant allergic reactions.

What is new in clinical research in contact dermatitis

The field of cutaneous allergy has enjoyed dynamic research advances in epidemiology and clinical contact dermatitis. Studies regarding outcomes analysis, validity, predictive value, and sensitivity have allowed clinicians to better understand the importance of patch test results. In the clinical arena, new and clinically relevant allergens are being discovered, such as corticosteroids, metals, preservatives, surfactants, and glues. Continued epidemiologic surveillance of new allergens will enable manufacturers to develop safer products for patients to use.