More than just methylisothiazolinone: Retrospective analysis of patients with isothiazolinone allergy in North America, 2017-2020.

BACKGROUND: Isothiazolinones are a common cause of allergic contact dermatitis. OBJECTIVE: To examine the prevalence of positive patch test reactions to isothiazolinones from 2017-2020 and characterize isothiazolinone-allergic (Is+) patients compared with isothiazolinone nonallergic (Is-) patients. METHODS: Retrospective cross-sectional analysis of 9028 patients patch tested to methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) 0.02% aqueous, MI 0.2% aqueous, benzisothiazolinone (BIT) 0.1% petrolatum, and/or octylisothiazolinone (OIT) 0.025% petrolatum. Prevalence, reaction strength, concurrent reactions, clinical relevance, and source of allergens were tabulated. RESULTS: In total, 21.9% (1976/9028) of patients had a positive reaction to 1 or more isothiazolinones. Positivity to MI was 14.4% (1296/9012), MCI/MI was 10.0% (903/9017), BIT was 8.6% (777/9018), and OIT was 05% (49/9028). Compared with Is-, Is+ patients were more likely to have occupational skin disease (16.5% vs 10.3%, P <.001), primary hand dermatitis (30.2% vs 19.7%, P <.001), and be >40 years (73.1% vs 61.9%, P <.001). Positive patch test reactions to >1 isothiazolinone occurred in 44.1% (871/1976) of Is+ patients. Testing solely to MCI/MI would miss 47.3% (611/1292) of MI and 60.1% (466/776) of BIT allergic reactions. LIMITATIONS: Retrospective cross-sectional study design and lack of follow-up data. CONCLUSION: Sensitization to isothiazolinones is high and concurrent sensitization to multiple isothiazolinone allergens is common.

Performance measurement part I: Foundational knowledge for measure development.

As medicine is moving toward performance and outcome-based payment and is transitioning away from productivity-based systems, value is now being appraised in healthcare through "performance measures." Over the past few decades, assessment of clinical performance in health care has been essential in ensuring safe and cost-effective patient care. The Centers for Medicare & Medicaid Services is further driving this change with measurable, outcomes-based national payer incentive payment systems. With the continually evolving requirements in health care reform focused on value-based care, there is a growing concern that clinicians, particularly dermatologists, may not understand the scientific rationale of health care quality measurement. As such, in order to help dermatologists understand the health care measurement science landscape to empower them to engage in the performance measure development and implementation process, the first article in this 2-part continuing medical education series reviews the value equation, historic and evolving policy issues, and the American Academy of Dermatology's approach to performance measurement development to provide the required foundational knowledge for performance measure developers.

Performance measurement part II: A guide to developing dermatology performance measures.

Throughout the 21st century, national and local governments, private health sectors, health insurance companies, healthcare professionals, labor unions, and consumers have been striving to develop an effective approach to evaluate, report, and improve the quality of healthcare. As medicine improves and health systems grow to meet patient needs, the performance measurement system of care effectiveness must also evolve. Continual efforts should be undertaken to effectively measure quality of care to create a more informed public, improve health outcomes, and reduce healthcare costs. As such, recent policy reform has necessitated that performance systems be implemented in healthcare, with the "performance measure" being the foundation of the system in which all of healthcare must be actively engaged in to ensure optimal care for patients. The development of performance measures can be highly complex, particularly when creating specialty-specific performance measures. To help dermatologists understand the process of creating dermatology-specific performance measures to engage in creating or implementing performance measures at the local or national levels, this article in the two-part continuing medical education series reviews the types, components, and process of developing, reviewing, and implementing performance measures.

Photopatch testing: Clinical characteristics, test results, and final diagnoses from the North American Contact Dermatitis Group, 2009-2020.

BACKGROUND: Photoallergic contact dermatitis (PACD) is a delayed hypersensitivity reaction to allergens only in the presence of ultraviolet radiation in sunlight. Photopatch testing (PhotoPT) is necessary to confirm the diagnosis of PACD. There are few published studies of PhotoPT in North America. OBJECTIVE: To summarise the results of patients photopatch tested by members of the North American Contact Dermatitis Group (NACDG), 2009-2020. METHODS: Retrospective analysis of patient characteristics and PhotoPT results to 32 allergens on the NACDG Photopatch Test Series. RESULTS: Most of the 454 tested patients were female (70.3%), 21-60 years old (66.7%) and White (66.7%). There were a total of 119 positive photopatch tests. Sunscreen agents comprised 88.2% of those, with benzophenones responsible for over half of them. Final diagnoses included PACD in 17.2%, allergic contact dermatitis (ACD) in 44.5%, polymorphous light eruption (PMLE) in 18.9% and chronic actinic dermatitis (CAD) in 9.0% of patients. CONCLUSIONS: In 454 patients with suspected photosensitivity referred for photopatch testing in North America, approximately one-fifth had PACD. Sunscreen agents, especially benzophenones, were the most common photoallergens. Other common diagnoses included ACD, PMLE and CAD. Photopatch testing is an important tool for differentiating these conditions.

Achieving consensus on patient-reported outcome measures in clinical practice for inflammatory skin disorders.

BACKGROUND: International Dermatology Outcome Measures and the American Academy of Dermatology recently agreed on a physician-reported global severity measure to demonstrate quality of care in inflammatory dermatoses. OBJECTIVE: Because patient-reported outcome measures are also important, we aimed to achieve consensus on 1 of these measures for clinical practice. METHODS: Patients and providers participated in a consensus-building study involving a modified-Delphi technique. Voting was focused on identifying a minimal set of assessments for clinical practice, patient global assessments (PtGAs), Skindex instruments, and final instrument selection for quality improvement. RESULTS: Among 53 stakeholders, >70% agreed that identification of patient goals, assessment of treatment harm, and assessment of the adequacy of treatment response were the minimal assessments needed for clinical practice. The most preferred PtGA was a 5-point PtGA (scale 0-4; 0 = clear, 4 = severe) having an optional check-box for worst ever. A new metric to assess change since treatment initiation, which we called a trajectory measure, was proposed. Stakeholders preferred Skindex instruments over PtGAs and a trajectory measure for clinical practice. LIMITATIONS: A small number of patients and caregivers were involved and a consensus was not reached on all items. CONCLUSION: PtGAs as standalone measures do not adequately capture the patient's assessment of disease severity or the effect of care. The combination of a PtGA with a Skindex instrument or another measure of health-related quality of life might provide a more comprehensive evaluation of patients in clinical practice.

Prevalence and trend of allergen sensitization in patients with cheilitis referred for patch testing, North American Contact Dermatitis Group data, 2001-2018.

BACKGROUND: An updated understanding of allergic contact cheilitis is needed. OBJECTIVES: To characterize clinical characteristics and allergen relevance in patients with cheilitis referred for patch testing. METHODS: Retrospective analysis of 43 772 patients patch tested with the North American Contact Dermatitis Group (NACDG) screening series from 2001 to 2018. RESULTS: Overall, 2094 patients (4.8%) had lips as one of three sites of dermatitis, 1583 (3.6%) had lips as the primary site and 1167 (2.7%) had lips as the sole site of dermatitis. Prevalences of cheilitis at any, primary, and sole sites significantly increased throughout the study cycle from 2001-2002 (2.7%, 2.2% and 1.7%) to 2017-2018 (7.8%, 5.2% and 3.7%). Approximately 60% of patients with any, a primary, or a sole site of cheilitis had one or more positive allergic patch-test reactions compared to 65% of those without cheilitis. CONCLUSION: Patients with cheilitis who were referred for patch testing had high rates of positive and relevant allergens. More than one in four patients with any, primary, or sole cheilitis had a positive reaction to non-NACDG screening allergens (28.0%, 26.8%, 31.1% vs. 21.6%) compared to patients without cheilitis, emphasizing the need for expanded patch test series in cheilitis.

An uncommon cause of swimmer's rash: Allergic contact dermatitis to persulfates in pools.

Allergic contact dermatitis (ACD) is an important diagnosis to consider in patients with dermatitis following specific exposures. Classically, ACD from persulfates is associated with hair-bleaching products and spa water/swimming pool exposure and is most commonly reported in adult men. We report a case of ACD to potassium peroxymonopersulfate (PPMS), a common pool "shocking" chemical, in a 7-year-old boy presenting with recurrent and diffuse dermatitis triggered by swimming pool exposure.

The 2021 annual report of DataDerm: The database of the American Academy of Dermatology.

The American Academy of Dermatology launched DataDerm in 2016 as the clinical data registry platform of the American Academy of Dermatology. DataDerm has evolved to be the largest database containing information about dermatology patients in the world. As of December 31, 2020, DataDerm contained data from 11.3 million unique patients and 40.0 million unique patient visits, with 782 practices representing 2290 clinicians actively participating in DataDerm. This article is the second in a series of annual reports about the status of DataDerm. While last year's 2020 first annual report presented the history of DataDerm as well as the rationale for its creation, maintenance, and expansion, this year's 2021 annual report presents the progress DataDerm has made over the past year along with its current status and future plans.

The completeness and accuracy of DataDerm: The database of the American Academy of Dermatology.

The utility of any database or registry depends on the completeness and accuracy of the data it contains. This report documents the validity of data elements within DataDerm, the clinical registry database of the American Academy of Dermatology. An external audit of DataDerm, performed by a third-party vendor, involved the manual review of 1098 individual patient charts from calendar year 2018 from 8 different dermatology practices that used 4 different electronic health records. At each site, 142 discrete data fields were assessed, comparing the data within DataDerm to the source data within the electronic health record. Audited data included 3 domains of data elements (diagnoses, medications, and procedures) and a performance measure ("Biopsy Reporting Time-Clinician to Patient"), which is 1 of several measures used by DataDerm as a Qualified Clinical Data Registry. Overall completeness of data was 95.3%, with a range among practices of 90.6% to 98.5%. Overall accuracy of data was 89.8%, with a range of accuracy among practices of 81.2% to 94.1%. These levels of completeness and accuracy exceed the rates in the literature for registries that are based on data that is extracted from electronic health records; and therefore, this audit validates the excellent quality of data in DataDerm.

Hand and foot dermatitis in patients referred for patch testing: Analysis of North American Contact Dermatitis Group Data, 2001-2018.

BACKGROUND: Dermatitis localized to hands (HD), feet (FD), or both hands and feet (HFD) has multiple etiologies, including atopic dermatitis, irritant contact dermatitis, and allergic contact dermatitis. Unfortunately, little is known about clinical differences between patients with HD, FD, and HFD. OBJECTIVE: To characterize differences in demographics, etiology, and patch testing results among patients presenting with HD, FD, or HFD referred for patch testing. METHODS: A retrospective analysis of patients patch tested by the North American Contact Dermatitis Group between 2001 and 2018. RESULTS: Of 43,677 patients who were patch tested, 22.8% had HD, 2.9% had FD, and 3.7% had HFD. Allergic and currently relevant patch test reactions to ≥1 North American Contact Dermatitis Group screening allergen occurred in similar proportions in all 3 study groups. However, HD (18.0%) had higher proportions of occupationally relevant reactions than HFD (8.9%) or FD (4.0%). Nickel and fragrance mix I were in the top 5 currently relevant allergens for HD, FD, and HFD. Other top allergens, as well as allergen sources, differed between HD, FD, and HFD. LIMITATIONS: No data on HD or FD morphology or distribution. CONCLUSION: HD, FD, and HFD have several differences with respect to patient characteristics, etiologies, and clinically relevant allergens.

Patch testing with glucosides: The North American Contact Dermatitis Group experience, 2009-2018.

BACKGROUND: Alkyl glucosides are nonionic surfactants that are increasingly used in personal care products. OBJECTIVE: To characterize positive patch test reactions to decyl glucoside (5% petrolatum, tested 2009-2018) and lauryl glucoside (3% petrolatum, tested 2017-2018). METHODS: Retrospective analysis of patients tested by the North American Contact Dermatitis Group. RESULTS: Of 24,097 patients patch tested to decyl and/or lauryl glucoside, 470 (2.0%) had positive reactions. Compared with glucoside-negative patients, glucoside-positive patients had higher odds of occupational skin disease (13.4% vs 10.1%; P = .0207), history of hay fever (38.5% vs 31.6%; P = .0014), atopic dermatitis (39.0% vs 28.6%; P < .0001), and/or asthma (21.8% vs 16.5%; P = .0023). Most glucoside reactions (83.9%) were currently relevant. The most common source was personal care products (63.0%), especially hair products (16.5%) and skin cleansers (15.2%). Of 4933 patients tested to decyl and lauryl glucoside, 134 (2.7%) were positive to 1 or both; 43.4% (43 of 99) of decyl-positive patients were also positive to lauryl glucoside and 55.1% (43/78) of lauryl glucoside patients were also positive to decyl glucoside. LIMITATIONS: The cohort predominantly reflects a referral population, and follow-up after testing was not captured. CONCLUSION: Glucoside positivity occurred in 2.0% of the tested patients. Reactions were often clinically relevant and linked to personal care products. Cross-reactivity was >40%.

Occupational contact dermatitis: Retrospective analysis of North American Contact Dermatitis Group Data, 2001 to 2016.

BACKGROUND: Patch testing is an important diagnostic tool for suspected allergic contact dermatitis (ACD) in occupational settings. OBJECTIVE: Provide an overview of occupational skin disease (OSD) and an analysis of occupational ACD in North American patients undergoing patch testing between 2001and 2016. METHODS: Patients with OSD were analyzed for frequency of allergic reactions to a screening series of allergens, occupational relevance, location of skin disease, and exposure sources. Demographic, occupation, and industry information were recorded. RESULTS: Of 38,614 patients evaluated, 4471 (11.6%) had OSD, of whom 3150 (70.5%) had ACD. The most common occupationally related allergens included rubber accelerators, preservatives, and bisphenol A epoxy resin. Hands (75.8%), arms (30.0%), and face (15.9%) were common sites of dermatitis. The occupations most affected were service workers and machine operators. LIMITATIONS: Our cohort may not reflect the general working population. CONCLUSION: This study identified common occupational allergens, exposure sources, and occupations/industries at risk. This information may help the clinician evaluate and manage patients with occupational contact dermatitis.

Patch testing with ammonium persulfate: The North American Contact Dermatitis Group Experience, 2015-2018.

BACKGROUND: Ammonium persulfate (APS), an oxidizing agent used in hair products, manufacturing, and pool/spa water, can cause skin reactions, including allergic contact dermatitis. OBJECTIVE: To characterize positive patch test reactions to APS (2.5% petrolatum). METHODS: Retrospective analysis of patients tested to the North American Contact Dermatitis Group screening series from 2015 to 2018. RESULTS: Of 10,526 patients, 193 (1.8%) had positive patch test reactions to APS. Compared with APS-negative patients, APS-positive patients were significantly more likely to be male (43.2% vs 28.0%; P < .0001); have primary hand dermatitis (30.2% vs 22.0%; P = .0064), scattered generalized dermatitis (25.5% vs 17.9%; P = .0064), or trunk dermatitis (8.9% vs 4.9%; P = .0123); and have dermatitis that is occupationally related (22.2% vs 10.9%; P < .0001). More than half of the APS-positive reactions were currently relevant (57.0%); 19 (9.8%) were related to occupation, especially hairdressers (68.4%). Swimming pools/spas (23.3%) and hair care products (19.2%) were the most common sources of APS. LIMITATIONS: Immediate reactions and follow-up testing were not captured. CONCLUSION: The proportion of patients positive to APS was 1.8%. APS positivity was significantly associated with male sex and hand dermatitis. Swimming pool/spa chemicals were important sources of APS exposure.

Age-related differences in patch testing results among children: Analysis of North American Contact Dermatitis Group Data, 2001-2018.

BACKGROUND: An updated understanding of allergic contact dermatitis is needed, particularly in children. OBJECTIVES: To compare positive and clinically relevant reactions in children versus adults referred for patch testing. METHODS: Retrospective analysis of 1871 children and 41,699 adults from the North American Contact Dermatitis Group (NACDG) from 2001-2018. RESULTS: Both final diagnosis of allergic contact dermatitis (55.2% versus 57.3%; chi square, P = .0716) and prevalence of ≥ 1 currently relevant reaction to a NACDG screening allergen (49.2% vs 52.2%; P = .1178) were similar between children and adults. Currently in children, the most common relevant allergens were nickel sulfate (17.3%), hydroperoxides of linalool (7.8%), methylisothiazolinone (7.7%), cobalt chloride (7.0%), and fragrance mix I (4.9%). Approximately a fifth of children had a positive reaction to a non-NACDG allergen. CONCLUSION: Over half of children referred for patch testing were diagnosed with allergic contact dermatitis. The most common relevant allergens in children were nickel sulfate, cobalt chloride, and hydroperoxides of linalool. Twenty percent of children had at least 1 positive reaction to allergens/substances not on the NACDG screening series, underscoring the need for comprehensive testing.

Medical adhesive allergens: Retrospective analysis of cross-sectional data from the North American Contact Dermatitis Group, 2001-2018.

BACKGROUND: Identification of allergens causing medical adhesive contact allergy is difficult. OBJECTIVE: To characterize the demographics, clinical characteristics, patch test results, and occupational data for North American Contact Dermatitis Group patients with medical adhesive contact allergy. METHODS: A retrospective study of 43,722 North American Contact Dermatitis Group patients patch tested from 2001 to 2018 with medical adhesive (tapes/bandaids/adhesive aids/suture glue) sources, positive patch test results, and final primary diagnoses of allergic contact dermatitis. RESULTS: In total, 313 (0.7%) patients met the inclusion criteria. Compared with other patients with final primary diagnoses of allergic contact dermatitis, patients with a medical adhesive allergy were less likely to be male (odds ratio, 0.58; 95% CI, 0.45-0.77) and/or aged >40 years (odds ratio, 0.76; 95% CI, 0.60-0.96). The most common North American Contact Dermatitis Group screening series allergens were colophony (80.7%), balsam of Peru (3.9%), 2-hydroxyethyl methacrylate (2.7%), and carba mix (2.7%). One-fourth of the patients (79/313, 25.2%) had positive patch test reactions to supplemental allergens/materials, and 54 (17.3%) of the 313 patients only had reactions to supplemental allergens/materials. LIMITATIONS: Results of comprehensive patch testing may be prone to referral population selection bias and may not be representative of the general dermatology population. CONCLUSION: Colophony was the most common allergen. Supplemental allergens and materials should be tested in the evaluation of a suspected medical adhesive contact allergy.

Patch testing with cobalt in children and adolescents: North American contact dermatitis group experience, 2001-2018.

BACKGROUND: Allergic contact dermatitis (ACD) to cobalt is more common in children and adolescents than adults. However, detailed information on sites and sources of cobalt ACD is limited. OBJECTIVES: To assess trends in positive and clinically relevant patch test reactions to cobalt in children and associated patient characteristics, common sources and body sites affected. METHODS: A retrospective analysis of children (<18 years) patch tested to cobalt by the North American Contact Dermatitis Group between 2001 and 2018. RESULTS: Of 1919 children patch tested, 228 (11.9%) and 127 (6.6%) had a positive/allergic or currently relevant patch test reaction to cobalt, respectively. The most common primary body sites affected were scattered generalized (30.0%), face, not otherwise specified (10.6%) and trunk (10.1%). Patients with allergic and currently relevant allergic patch test reactions were more likely to have a primary site of trunk (p = 0.0160 and p = 0.0008) and ears (p = 0.0005 and p < 0.0001). Affected body site(s) varied by cobalt source among patients with currently relevant reactions, especially for less common sources. The most commonly identified sources of cobalt included jewellery, belts and clothing. CONCLUSIONS: Positive patch test reactions to cobalt were common in children. The most common body site was scattered generalized and the sources of cobalt varied by body site.

Occupational dermatitis to facial personal protective equipment in health care workers: A systematic review.

BACKGROUND: Prolonged wear of facial protective equipment can lead to occupational dermatoses. OBJECTIVE: To identify important causes of occupational dermatoses from facial protective equipment. METHODS: A systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was performed using PubMed and Embase databases. Articles were included if they reported occupational dermatoses caused by surgical/procedure masks or N95 respirators, or both. RESULTS: We identified 344 articles, and 16 were suitable for inclusion in this review. Selected articles focused on facial occupational dermatoses in health care workers. Allergic contact dermatitis to the elastic straps, glue, and formaldehyde released from the mask fabric was reported. Irritant contact dermatitis was common on the cheeks and nasal bridge due to pressure and friction. Irritant dermatitis was associated with personal history of atopic dermatitis and prolonged mask wear (>6 hours). Acneiform eruption was reported due to prolonged wear and occlusion. Contact urticaria was rare. LIMITATIONS: Only publications listed in PubMed or Embase were included. Most publications were case reports and retrospective studies. CONCLUSION: This systematic review from members of the American Contact Dermatitis Society highlights cases of occupational dermatitis to facial protective equipment, including potential offending allergens. This work may help in the diagnosis and treatment of health care workers with facial occupational dermatitis.

Contact dermatitis to personal care products is increasing (but different!) in males and females: North American Contact Dermatitis Group data, 1996-2016.

BACKGROUND: Personal care products (PCPs) are commonly responsible for allergic contact dermatitis and irritant contact dermatitis. PCP use was historically associated with females, but male-targeted PCPs are increasingly being marketed. OBJECTIVE: To characterize and compare males with PCP-related contact dermatitis (MPCPs) and females with PCP-related contact dermatitis (FPCPs). METHODS: This was a retrospective cross-sectional analysis of North American Contact Dermatitis Group data (1996-2016). RESULTS: Four thousand six hundred eighty of 16,233 men (28.8%) and 12,730 of 32,222 (39.5%) women had a PCP identified as a source of irritant contact dermatitis or a positive patch test reaction. The proportion of PCP-related dermatitis in both sexes significantly increased (>2.7-fold) over the decade of study. Compared with FPCPs, a larger proportion of MPCPs were older or had trunk or extremity dermatitis (P < .0001). MPCPs were twice as likely to have soaps as a source while FPCPs were twice as likely to have hair care products (P < .0001). The most common PCP-related North American Contact Dermatitis Group allergens for both sexes were methylisothiazolinone (MPCP 28.8% and FPCP 21.5%), fragrance mix I (MPCP 22.3% and FPCP 20.1%), balsam of Peru (MPCP 18.5% and FPCP 14.1%), quaternium-15 (MPCP 16.1% and FPCP 12.3%), and paraphenylenediamine (MPCP 11.5% and FPCP 11.1%). LIMITATIONS: Patient population referred for suspected contact dermatitis. CONCLUSIONS: PCP-related dermatitis is increasing. Sites of involvement and relevant PCP sources are distinct between sexes. Male and female variation in exposure history may explain differences in reactivity to some allergen groups.

Scalp involvement in patients referred for patch testing: Retrospective cross-sectional analysis of North American Contact Dermatitis Group data, 1996 to 2016.

BACKGROUND: Scalp conditions are often multifactorial. OBJECTIVE: To characterize patients with scalp involvement and patch-testing outcomes. METHODS: Retrospective cross-sectional analysis of North American Contact Dermatitis Group data (1996-2016). Study groups included patients with scalp involvement (≤3 anatomic sites coded) with or without additional sites. RESULTS: A total of 4.8% of patients (2331/48,753) had scalp identified as 1 of up to 3 affected anatomic sites. Approximately one-third of "scalp-only" individuals had a specific primary diagnosis of allergic contact dermatitis (38.6%), followed by seborrheic dermatitis (17.2%) and irritant contact dermatitis (9.3%). When adjacent anatomic sites were affected, allergic contact dermatitis was more frequently identified as the primary diagnosis (>50%). The top 5 currently clinically relevant allergens in scalp-only patients were p-phenylenediamine, fragrance mix I, nickel sulfate, balsam of Peru, and cinnamic aldehyde. Methylisothiazolinone sensitivity was notable when adjacent anatomic sites were involved. The top 3 specifically identified sources for scalp-only allergens were hair dyes, shampoo/conditioners, and consumer items (eg, hair appliances, glasses). LIMITATIONS: Tertiary referral population. CONCLUSION: Isolated scalp involvement was less likely to be associated with allergic contact dermatitis than when adjacent anatomic sites were involved. Overlap with multiple diagnoses was frequent, including seborrheic dermatitis, irritant dermatitis, other dermatoses, or all 3. p-Phenylenediamine was the most common allergen.

Hand dermatitis in adults referred for patch testing: Analysis of North American Contact Dermatitis Group Data, 2000 to 2016.

BACKGROUND: Hand eczema (HE) is a heterogeneous and burdensome disorder. OBJECTIVE: To characterize the clinical characteristics, etiologies and allergen relevance in adults with HE referred for patch testing. METHODS: Retrospective analysis (2000-2016) of North American Contact Dermatitis Group data (n = 37,113). RESULTS: Overall, 10,034 patients had HE, with differences of overlap between allergic contact, irritant contact, and atopic dermatitis. Allergic contact HE fluctuated, whereas atopic HE steadily increased, and irritant HE decreased over time. HE was associated with higher proportions of positive patch tests (67.5% vs 63.8%; χ2, P < .0001). The five most common clinically relevant allergens were methylisothiazolinone, nickel, formaldehyde, quaternium-15, and fragrance mix I. HE was associated with significantly higher odds of positive patch test reactions and clinical relevance in 13 and 16 of the 25 most common allergens, respectively, including preservatives, metals, topical medications, and rubber accelerators. LIMITATIONS: No data on HE phenotype. CONCLUSION: HE in adults was associated with higher proportions of positive patch tests, with a heterogeneous profile of allergens. Patch testing remains an important tool in the evaluation of patients with HE.