Patch Test Reactions Research Articles

Immune response to topical sodium lauryl sulfate differs from classical irritant and allergic contact dermatitis.

Sodium lauryl sulfate (SLS) is used as a control irritant in patch testing for allergic contact dermatitis (ACD). However, up to 20% of those tested react to SLS, whereby the pathophysiological basis of this reaction is still unclear. To mimic patch test reactions, we repeatedly applied SLS to the skin of wild-type mice. Reactions were compared with those in a classical ACD model induced by oxazolone and an irritant contact dermatitis (ICD) model induced by croton oil. Skin inflammation was assessed with ear thickness measurements, immunohistochemistry, qRT-PCR, and flow cytometry. Topical SLS treatment was further investigated in Flg/Hrnr-/-, Myd88/Tlr3-/-, and Rag1-/- mouse models. All three compounds caused ear swelling with different courses. Oxazolone treatment, compared with the ICD model, resulted in a greater influx of immune cells (CD4+, MHCII+, CD11b+). Similarly, SLS did not induce immune cell infiltration or expression of selected inflammatory and regulatory cytokines. SLS induced the most pronounced keratinocyte proliferation. Compared with wild-type mice, topical SLS application did not increase ear swelling in skin barrier deficient Flg/Hrnr-/- mice, but led to significantly delayed swelling in mice with defects in innate or adaptive immune functions (Myd88/Tlr3-/-, Rag1-/-). SLS-induced contact dermatitis differed from classical ACD and ICD, as it elicited less pronounced immune alterations. Skin barrier impairment does not affect SLS-induced contact dermatitis, whereas both innate and adaptive components are involved in SLS skin reactions.

The Clinical Phenotype of Patients with Contact Polysensitization, a Retrospective Cohort.

Background: Polysensitization, defined as contact sensitization to three or more allergens, is an allergic phenotype with a common genetic background. Our study aims to characterize the clinical features of patients with polysensitization. Methods: We analyzed patch test results of 5,082 patients from a designated contact dermatitis clinic in Tel Aviv between 2012 and 2022 and compared the polysensitized group with nonsensitized and oligosensitized patients, hence patients reacting to 1 or 2 allergens. Results: About 8.5% of patients were polysensitized. In the nonsensitized group, there were significantly fewer female patients and more children (P < 0.05) than in the polysensitized group. Asthma prevalence was linearly associated with the number of positive reactions in patch test. Polysensitized patients were more commonly suffering from hand eczema and an occupational etiology (P < 0.05). Textile dye mix, lyral, fragrance mix II, formaldehyde, colophonium, and p-phenylendiamine were more common sensitizers among the polysensitized group, whereas nickel sulfate, 2-hydroxyethyl methacrylate, fragrance mix 1, p-tert-butylphenol formaldehyde resin, and sodium metabisulfite were more common among the oligosensitized group. Conclusions: The association between polysensitization, asthma prevalence, and sensitization to volatile allergens raises an intriguing clinical phenotype. Further mechanistic studies are needed in this regard.

Comparison of patch testing Brazilian (Green) propolis and Chinese (poplar-type) propolis: Clinical epidemiological study using data from the Information Network of Departments of Dermatology (IVDK).

Propolis types differ regarding their chemical composition. To compare patch test results based on Brazilian (Green) propolis with data based on Chinese (poplar-type) propolis, and to evaluate the specifications of raw materials used for the PT preparations. In the Information Network of Departments of Dermatology (IVDK), 1290 consecutive patients were patch tested with Brazilian (Green) propolis (NH400, SmartPractice Europe). Patch test reactivity was compared with results obtained with Chinese (poplar-type) propolis (NA71, SmartPractice Europe) by calculating frequencies and corresponding 95% confidence intervals. Data on the specifications of raw materials used for NH400 and NA71 were obtained from the manufacturer. Positive reactions to NH400 were found in 303 (23.5%) patients with unclear clinical relevance in most cases. Patients reacting to NH400 were less often sensitised to fragrances and colophony, but more often to nickel sulphate and cobalt chloride than patients reacting to NA71. The NH400 batch used contained high levels of aerobic bacteria, and was not purified by ethanolic extraction. Pattern of concomitant reactivity along with raw material properties suggests that the high frequency of positive reactions to NH400 may primarily result from bacterial contamination or impurities in the PT preparation rather than from propolis constituents.

The value of patch testing with plants "as is" in diagnosing plant sensitization.

The number of commercially available plant allergens/extracts is limited and therefore patch testing with fresh/dried plant material may be a necessary supplement in diagnosing plant allergy. To evaluate the usefulness of patch testing with plants "as is" compared to patch testing with commercial and in-house produced plant test materials and to report on species eliciting positive patch test reactions. Consecutive eczema patients, who were patch tested between January 2019 and December 2023 and who had at least one positive reaction to a plant allergen and/or extract and/or plant "as is" were included in the study. A total 57 out of 1893 patients tested (3%) were sensitised to plants. Compositae plants were the most frequent sensitizers, followed by tomato, tulipalin A, falcarinol, and Philodendron plants. In 12 patients (21%), the diagnosis was based on patch testing with fresh plants only. Occupational sensitization occurred in 32%. Other sensitizers included Hydrangea, Pelargonium zonale, and Monstera. A large minority of plant-sensitised patients would have been undiagnosed without patch testing with plants "as is." Most of the culprit plants were known sensitizers, but not commercially available, and these and new species taken into cultivation makes patch testing with fresh plants unavoidable and worthwhile.

Hand eczema in Italian patients referred for patch testing: A retrospective SIDAPA study (2016-2023).

Hand eczema (HE) is a common skin disease with a negative impact on patients' quality of life in occupational and non-occupational settings. Up-to-date, data on HE in Italian patients referred for patch testing are lacking. To characterise the profile in terms of demographics, aetiology and patch test results of Italian patients affected by HE referred for patch testing. A retrospective descriptive study on consecutive patients affected by HE who underwent patch testing from 2016 to 2023 in eight dermatology clinics was performed. HE patients were divided into two groups according to the exclusive (HE-only group) and not-exclusive (HE+ group) hand involvement, and compared to patients with eczema localised in body areas other than hands (NHE group). One thousand five hundred and ninety-seven patients were affected by HE (35.3% males; mean age 42.7 years), 60.2% belonging to the HE-only group and 39.8% to the HE+ group. Occupational dermatitis was diagnosed in 33.2% of HE-only patients, 25.0% of HE+ patients and 5.2% of NHE patients (p < 0.001). HE-only patients presented: Allergic Contact Dermatitis (ACD), Irritant Contact Dermatitis (ICD), atopic HE in 48.1%, 47.5% and 7.1%, respectively; hyperkeratotic palmar, acute recurrent vesicular and nummular clinical subtypes in 52.2%, 43.9% and 11.9%, respectively; relevant positive patch test reactions in 48.1% (nickel sulphate 18.9%, methylchloroisothiazolinone/methylisothiazolinone 10.6%, methylisothiazolinone 8.6%, p-phenylenediamine 6.0% and potassium dichromate 4.7%). HE patients, and particularly those with exclusive hand involvement, show a particular profile in terms of demographic and clinical characteristics, etiologies and relevant positive patch test reactions.

High prevalence but no current clinical relevance of methyldibromo glutaronitrile since its ban in Turkey in 2015.

Regulatory actions significantly reduced methyldibromo glutaronitrile (MDBGN)-induced allergic contact dermatitis (ACD) from cosmetics in Europe. Turkey banned MDBGN in 2015. To assess sensitization and ACD rates to MDBGN before and after its ban in Turkey. Data from 2653 consecutively patch tested patients between 1996 and 2023 with MDBGN 0.1% pet. (n = 573) or 0.2%-0.3% pet. (n = 1310) or 0.5% pet. (n = 770) were analysed. MDBGN was tested as MDBGN/phenoxyethanol (PE) in 1434 patients. The sensitization prevalence was 1.7% (45/2653), peaking at 5.3% in 2018 and 2023 with MDBGN 0.3% pet. There was a two-fold male predominance, with patients exclusively ≥20 years old. None of the patients reacted to PE. ACD occurred in 0.7% (19/2653), mainly affecting hands and linked to non-occupational exposure (78.9%), particularly from rinse-off/leave-on cosmetics. The pattern of 'middle-aged men with hand eczema and fragrance allergy' was particularly notable. Occupational ACD was rare (21.1%), occurring mainly in hairdressers from hair gel. Positive reactions with current clinical relevance dropped from 48.3% (1996-2014) to zero after 2015 (p < 0.001). The ban effectively reduced MDBGN-induced ACD in Turkey, yet the prevalence of positive patch test reactions remains high, likely due to past exposures or other undisclosed sources. We suggest continued testing of MDBGN in the EBS in Turkey.

Supplemental Patch Testing Identifies Allergens Missed by Standard Screening Series.

Background: Supplemental patch testing is an adjunct to standard patch test screening series. Objective: To determine the demographics, characteristics, frequency, relevance, and interpretation of patch test reactions for supplemental patch testing. Methods: Retrospective study of patients tested 2017-2020 with North American Contact Dermatitis Group (NACDG) and supplemental screening series (Supplemental Series A [SSA], Supplemental Series B [SSB]). Demographics, characteristics, reaction strengths, relevance, and final interpretation were recorded. Results: Cohort included 791 patients; 73.5% female, 68.6% age >40 years. 74.1% were White, 15.2% Black, 5.7% Asian, and 1.5% Hispanic. The most common Dermatitis sites were scattered/generalized (27.2%), face (24.0%), and hands (23.5%). For 2017-2018 and 2019-2020, respectively, 82% (318/388) and 78.4% (316/403) had ≥1 "allergic" reaction. In addition, 13.5% (52/385) and 11.7% (47/403) had SSA reactions, and 38.1% (115/302) and 31.5% (101/321) had SSB reactions. In the 87 (2017-2018) and 99 (2019-2020) patients with negative NACDG testing, 17 (19.5%) and 12 (12.1%) had supplemental reactions. Of the 34 supplemental allergens with reaction frequency ≥1%, 58.8% (20/34) are not part of the American Contact Dermatitis Society 90 (2020) or NACDG 2021-2022 screening series. The highest frequency allergens from this group were dodecyl and octyl gallate, cinnamic alcohol, phenyl salicylate, hexahydro-1,3,5-tris-(2-hydroxyethyl) triazine, and abitol. Conclusions: Supplemental patch testing identifies additional relevant allergens in patients with suspected allergic contact Dermatitis.

Occupational Contact Dermatitis in Construction Workers: A Retrospective Analysis of the North American Contact Dermatitis Group Data, 2001-2020.

Background: Construction workers (CWs) are at risk for occupational contact dermatitis (CD) owing to workplace exposures. Objective: Determine the prevalence of occupational allergic CD and characterize common occupational allergens in CWs referred for patch testing in the United States and Canada. Methods: Retrospective cross-sectional analysis of patients patch tested by the North American Contact Dermatitis Group from 2001 to 2020. Results: Of 47,843 patch-tested patients, 681 (1.4%) were CWs. Compared with non-CWs, CWs were more likely to be male (91.0% vs 30.9%) have occupational skin disease (36.9% vs 11.4%) and have hand involvement (37.2% vs 22.5%) (all P < 0.0001). Of 681 CWs, 60.1% (411) had clinically relevant positive patch test reactions, and nearly 1/3 of CWs (128) had occupationally relevant reactions. Most common occupationally relevant allergens were potassium dichromate 0.25% pet. (30.5%, 39/128), bisphenol A epoxy resin 1% pet. (28.1%, 36/128), carba mix 3% pet. (14.8%, 19/128), cobalt (ii) chloride hexahydrate 1% pet. (14.1%, 18/128), and thiuram mix 1% pet. (14.1%, 18/128). Top sources of occupationally relevant allergens were cement/concrete/mortar (20.4%, 46/225), gloves (15.1%, 34/225), and coatings (paint/lacquer/shellac/varnish/stains) (9.8%, 22/225). Conclusions: Occupational CD in North American CWs is common. In this group, frequently identified etiological sources of occupational allergic CD included metals, epoxy resin, and rubber.

Contact sensitization and self-reported eczema in Swedish painters with occupational exposure to isothiazolinones.

Due to an increasing occupational usage of isothiazolinone (IT)-containing preservatives, and their potential to cause skin sensitization and allergic contact dermatitis, that is, chronic disease, there is a need for more knowledge on how highly exposed workers are affected. The overall objective was to explore dermatological symptoms of potentially long-lasting or chronic character in Swedish painters. Building painters from western and southern Sweden were initially invited to perform a questionnaire on occurrence of skin symptoms. Participants with affirmative responses, and the right inclusion criteria, were further invited to patch testing with four different ITs: benzisothiazolinone (BIT), methylisothiazolinone, methylchloroisothiazolinone and octylisothiazolinone. There was a tendency towards higher occurrence of positive patch test reactions among the painters compared with occupationally unexposed registry patients; however, not statistically significant differences. BIT was the substance most frequently causing positive test results in both groups. The occurrence of adult-onset eczema was higher in painters than in the control group of electricians, and just shy of statistical significance concerning any of several skin locations (face/legs/arms/hands). Building painters present with positive patch test reactions to common paint preservatives (ITs), and they report adult-onset eczema more often than do less occupationally exposed groups.

Clinico-epidemiological and Patch Test Profile of Patients with Suspected Allergic Contact Dermatitis to Cosmetics in a Tertiary Care Hospital in the Southern Philippines: A 3-year Retrospective Study

Background: Allergic contact dermatitis (ACD) is a common skin inflammatory reaction occurring at the site of challenge with a contact allergen in sensitized individuals and one of the most common causes for consultation in dermatology clinics. Patch testing is a method for detecting the causative component in suspected cases of ACD. Awareness about the causative allergen aids in reducing morbidity and can significantly minimize the impact of ACD in the affected people. Objectives: The study aimed to measure the number of relevant positive reactions in patch tests being performed in our institution in patients with ACD to cosmetic products. Methods: A total of 60 patients who were diagnosed with ACD to cosmetics and underwent patch testing were reviewed to identify the clinico-epidemiological and patch test profiles of these patients. Results: The study showed that the mean age of patients was 42 comprising mostly of females. Most of the patients were unemployed, office workers, and medical workers. The most common cosmetic products that caused ACD include soaps, shampoos, lotions, and moisturizers. Nickel is still the most tested positive among these patients, followed by fragrance mixes and 4-phenylenediamine base. They are widely distributed in cosmetic products, especially in soaps and lotions. The pattern of dermatitis revealed facial dermatitis to be the most common reason for consult of these patients. Conclusion: Patch test is valuable in the setting of establishing the etiology of ACD to cosmetic products.

The Contact Sensitivity of Turkish Children and Adolescents to European Baseline Series Allergens between 2013 and 2023.

Increasing the numbers of patch testing in suspected children increases the rate of diagnosis of allergic contact dermatitis and the identification of clinically relevant allergens. The aim of this study was to identify the most frequently observed allergens among Turkish children and adolescents patch-tested in 2013-2023. The patch test results of 160 patients (age ≤18) were analyzed retrospectively. The frequency of contact allergens and distribution of positive results in terms of sex, age group (children and adolescents), and the presence of atopic dermatitis (AD) were identified. Forty-nine patients (30.6%) (34 girls and 15 boys) exhibited positive patch test reactions to a minimum of one allergen, and contact sensitivity was statistically significantly higher in girls (P=0.034). The five most frequent allergens were nickel sulfate (10.6%), MCI/MI (8.1%), cobalt chloride (5.6%), p-phenylenediamine (PPD) (5%), and MI (3.5%). No significant association was observed between patch test positivity and age groups (P>.05). Nickel sulfate sensitivity was significantly higher in girls than in boys (P=.043). A positive reaction was detected in 31.3% of patients with AD and in 33.7% of those without (P>.05), and a statistically significant relationship was observed between contact sensitivity to fragrance allergens and AD (P=.046). Metals and preservatives represent the most frequent allergens in Turkish children and adolescents. Metal sensitivity is expected to decrease as legislation is enforced. Regulatory measures are now required to reduce MI and MCI/MI contact allergy in Turkey.

Clinical relevance of doubtful reactions in patch testing: A single-centre retrospective study.

Doubtful reactions in patch testing are infrequently reported in the literature; however, recent reports have suggested they be assessed with the same scrutiny as stronger reactions. Assess the clinical relevance of doubtful reactions in patch testing. Retrospective study of 1514 patients comprehensively patch tested via the NACDG standard series and additional allergens based on history. The clinical relevance of each reaction was graded based on the NACDG scale: definite, probable, possible, past, unknown and irritant. Reactions were considered 'unique' if an additional mild-to-strong reaction to the same chemical at a different concentration was not observed. 68.9% (1043) of patients demonstrated at least 1 doubtful reaction. Of 4453 total doubtful reactions, 92.2% (4106) were unique. Only 3.3% (137) and 12.2% (500) of these were determined to be of definite or probable clinical relevance respectively. 'Fragrance' was the most common allergen family present among the unique definite doubtful reactions (37). However, 24 (64.9%) of these also had a stronger reaction to another fragrance. Cocamidopropyl betaine was the second most frequent allergen demonstrating definite doubtful reactions (27) and unique in 85.2% (23) of cases. Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) was most prevalent (36) but less frequently unique (58.3%, 21). Doubtful reactions may not be as impactful to clinical decision making as theorised in the literature. Few demonstrate definite clinical significance, and many have related stronger reactions that capture them for clinical purposes. Identification of doubtful reactions to cocamidopropyl betaine and MCI/MI may be of greatest significance as they most frequently were not supported by stronger reactions.

Allergic Contact Dermatitis to Linalool Hydroperoxides: Pitfalls in the Diagnostic Process-Findings from a Repeated Open Application Test Study.

Background: Increasing trends of oxidized linalool contact allergy have been reported. However, the impact of reactivity and dose in eliciting allergic contact Dermatitis caused by linalool hydroperoxides is insufficiently investigated. Objectives: To perform repeated open application tests (ROATs) using the real-world concentrations of linalool hydroperoxides in patients and control participants. Materials and Methods: Patients who previously had a positive (patients) and a negative (controls) patch test reaction to linalool hydroperoxides 1.0% in petrolatum were patch tested with a dilution series of linalool hydroperoxides preparations and asked to perform ROAT twice daily with 3 concentrations of linalool hydroperoxides creams and a negative control cream for 28 days. The creams contain 44, 140, and 440 PPM of linalool hydroperoxides, representing real-world doses reported in consumer products. Results: Of all 47 participants, 31 were linalool hydroperoxides contact allergy patients, and 16 were controls. One patient had a positive ROAT reaction in the area where cream at the highest concentration of linalool hydroperoxides was applied for 28 days. Conclusions: Repeated exposure to creams containing linalool hydroperoxides at real-life concentrations could rarely elicit an allergic reaction on intact skin after 4 weeks.

2-Hydroxyethyl methacrylate (2-HEMA) sensitization, a global epidemic at its peak in Spain?

A global epidemic of allergic contact dermatitis to (meth)acrylates has been described in relation to the widespread use of manicure products. To evaluate the frequency of sensitization to 2-hydroxyethyl methacrylate (2-HEMA) among consecutively patch tested patients with eczema in Spain; the percentage of current relevance; the MOAHLFA index; and, the potential sources of exposure to (meth)acrylates. From January 2019 to December 2022, 2-HEMA 2% pet. was prospectively patch tested in 24 REIDAC (Spanish Allergic Contact Dermatitis Registry) centres. Six thousand one hundred thirty-four patients were consecutively patch tested with 2-HEMA 2% pet. 265/6134 (4.3%) were positive. Positive reactions of current relevance were identified to involve 184/265 (69%). The efficiency (number of patch tests needed to detect relevant positive patch test reactions) was 34 (6134/184). The variable 'occupational' was found to be significantly associated with a higher risk for relevant positive reactions to 2-HEMA (OR: 10.9; 95% CI: 8.1-14.9). (Meth)acrylate sensitization is a prevalent health issue in Spain. 2-HEMA 2% pet. has been identified to be a highly effective (meth)acrylate allergy marker in the GEIDAC baseline series. The responsible authorities should implement policies guaranteeing accurate labelling of industrial, medical, and consumer materials while ensuring the enforcement of said labelling through appropriate legal means.

Allergic or Not: Final Interpretation of Doubtful Patch Test Reactions From the North American Contact Dermatitis Group, 2019-2020.

Background: Doubtful patch test reactions generally do not meet criterion for positivity in patch testing. However, the North American Contact Dermatitis Group (NACDG) allows for doubtful reactions to be coded with a final determination of "allergic/positive" based on the temporal pattern, appearance, known characteristics of the allergen, and/or other supportive patch test reactions. Objectives: To analyze NACDG data from the 2019-2020 patch test cycle to identify patterns in the interpretation and relevance of doubtful reactions. Methods: The frequency and proportions of doubtful reactions were tabulated and analyzed for patterns. Statistical analyses were limited to allergens with ≥30 doubtful reactions to ensure adequate sample size. Results: Of patch-tested patients, 31.9% (1315/4121) had ≥1 doubtful reaction. Of 2538 total doubtful reactions, 46% (n = 1167) had a final interpretation of "allergic/positive." The allergens with the highest proportion of doubtful reactions at the final visit were hydroperoxides of linalool 1% (4.5%), fragrance mix I 8.0% (3.9%), and cetrimonium chloride 0.5% (3.4%). Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) 0.02% (P < 0.001), MI 0.2% (P < 0.001), nickel sulfate hexahydrate 2.5% (P = 0.001), and neomycin sulfate 20.0% (P = 0.003) doubtful reactions were more likely to be interpreted as allergic than nonallergic. Methyldibromoglutaronitrile/phenoxyethanol 0.2% (P < 0.001), oleamidopropyl dimethylamine 0.1% (P < 0.001), formaldehyde 2.0% (P < 0.001), cetrimonium chloride 0.5% (P < 0.001), benzophenone-4 (sulisobenzone) 10% (P < 0.001), iodopropynyl butylcarbamate 0.5% (P < 0.001), cocamidopropyl betaine 1.0% (P = 0.002), and benzisothiazolinone 0.1% (P = 0.012) doubtful reactions were less likely to be interpreted as allergic. Of the 1167 doubtful reactions interpreted as allergic, 84.9% had current relevance. Conclusions: Doubtful reactions were common and approximately one half were coded with a final interpretation of "allergic/positive." Of those, most were clinically relevant. MCI/MI, MI, nickel, and neomycin were more likely to be interpreted as allergic.

Gene profiling in active dermatitis lesions strengthens the diagnosis of allergic contact dermatitis

BackgroundDistinguishing between allergic and non-allergic forms of Contact Dermatitis (CD) is challenging and requires investigations based on patch-testing. Early detection of allergy biomarkers in active CD lesions could refine and simplify the management of CD patients. ObjectiveTo characterize the molecular signatures of active CD lesions. MethodsWe studied the expression of 12 allergy biomarkers by qRT-PCR in active lesions of 38 CD patients. Allergic CD (ACD) was diagnosed based on patch-test (PT) results and exposure assessment. Molecular signatures of active lesions, as well as positive PT reactions, were compared with those of reference chemical allergens and irritants. Results19 of the 38 CD patients reacted positively upon patch-testing and exposure assessment confirmed ACD diagnosis for 17 of them. Gene profiling of active CD lesions revealed two distinct molecular patterns: patients harboring signatures similar to reference allergens (n=23) or irritants (n=15). Among the 23 patients with an “allergy signature”, we found the 17 patients with confirmed ACD, while no culprit allergen was identified for the 6 other patients. Interestingly, the 15 patients without biomarker induction had negative PT, suggesting that they developed non-allergic CD reactions. ConclusionMolecular signatures from active skin lesions may help to stratify CD patients and predict those suffering from allergic contact dermatitis.

Contact allergens in African countries: A review of published patch test studies

AbstractOnly few studies on contact allergy in African countries have been published. The aim of the present study was to provide an overview of the most common contact allergens identified by the use of patch tests in African countries based on a review of the existing literature. A total of twenty‐four publications from eight African countries were initially identified by search in PubMed. The abstracts and method sections were screened, and 15 studies in which patch tests were actually used to identify the allergen causing the allergic contact dermatitis (ACD) were finally selected. Nickel, cobalt, chromium, fragrance mix and p‐tert‐butylphenol‐formaldehyde resin were the dominating contact allergens responsible for 40%–90% of the positive patch test reactions. This study indicates that a targeted effort directed towards prevention, avoidance and regulation of reliably identified contact allergens could reduce the disease burden of ACD considerable in some African countries.

Patch Testing With Nickel, Cobalt, and Chromium in Patients With Suspected Allergic Contact Dermatitis.

Background: Allergic contact dermatitis is frequently caused by metals, including multiple metals simultaneously. Objectives: To assess characteristics and associations of positive and clinically relevant patch test (PT) reactions with solitary and concurrent metal sensitization. Methods: A retrospective analysis of PT results for nickel, cobalt, and/or chromium from the North American Contact Dermatitis Group between 2001 and 2018 (n = 43,522). Results: 18.0% had a positive/allergic reaction to nickel sulfate hexahydrate, 7.3% to cobalt chloride hexahydrate, and 3.0% to potassium dichromate. 87.9% patients had a currently relevant reaction to 0, 9.4% to 1, and 2.7% to multiple metals tested. Patients with 1 versus no currently relevant reactions to metal were more likely to have a primary dermatitis site of trunk, feet, and ears; patients with currently relevant reactions to multiple metals had more dermatitis affecting the trunk and ears. Metal sources varied by co-reacting metal, especially for patients with cobalt and chromium allergy. Jewelry was the most commonly identified source of nickel and cobalt for both solitary and concurrent metal allergy. Conclusions: Sensitization to multiple metals occurred in 6% of patients. Allergen sources varied between patients with sensitivity to 1 metal versus those who had concurrent sensitivity to cobalt and/or chromium.

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

Isothiazolinones are a common cause of allergic contact dermatitis. 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. 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. 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 >40years (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. Retrospective cross-sectional study design and lack of follow-up data. Sensitization to isothiazolinones is high and concurrent sensitization to multiple isothiazolinone allergens is common.

Impact of dupilumab on patch test results and allergic contact dermatitis: A prospective multicenter study

Limited and conflicting data have been reported on the impact of dupilumab (DUPI) on patch test (PT) results and its efficacy against allergic contact dermatitis (ACD). This study was undertaken to analyze PT reactivities and relevance during treatment with DUPI to determine whether they could detect ACD in patients with uncontrolled or worsened atopic dermatitis (AD) who were receiving this agent. This prospective, multicenter study examined 76 DUPI-treated patients who had undergone PTs. The relevant information was collected during 3 visits. Overall, 36 patients (47%) had ≥1 positive PT reaction, and 142 PT results were positive. Twenty-three patients (30%) had ≥1 positive and clinically relevant PT result. Five of them had clinical eczema improvement after allergen avoidance. We compared the PT results of 36 patients before and during DUPI therapy, representing 1230 paired PT allergens, of which 1022 were the same, 34 were positive, 44 were lost, and 130 were uninterpretable. Because the number of patients included remains limited, our findings should be confirmed with a larger sample. Our results confirmed the usefulness of PTs for patients receiving DUPI, with good PT reproducibility. We suggest that all DUPI-treated patients with AD developing partial responses or experiencing symptom worsening should undergo PTs to look for contact sensitization.