Jeanne Duus Johansen

Background: Gold sensitization is common, but its clinical and immunologic significance remains unclear. European data from consecutively patch tested patients are scarce. Animal models suggest that gold can induce systemic autoimmunity, but studies in humans are limited. Objectives: To characterize gold sodium thiosulphate (GST) patch test positive patients, including co‐sensitization patterns to other metals and determine whether gold sensitization is linked to autoimmune diseases. Methods: A retrospective register‐based study including 3436 dermatitis patients consecutively patch tested between 2015 and 2024 at Odense University Hospital, Denmark. Patch test results were linked to diagnostic data from the Danish National Patient Registry. Autoimmune diseases were grouped into six categories analysed using logistic regression. Results: Gold sensitization was found in 18.7% of tested patients and was more common in women (OR 2.38, 95% CI 1.96–2.94) and at an age above 40 years (OR 1.32, 95% CI 1.09–1.60). Concomitant sensitization to Ni, Cr and Co increased with higher gold reactivity ( p < 0.01). No association was observed between gold sensitization and autoimmune diseases, overall (OR 1.00, 95% CI 0.82–1.22). Conclusions: A positive patch test to GST was associated with other metal allergies but not with any autoimmune diseases.

Background: Hairdressers frequently perform wet work, which weakens the skin barrier. Repeated skin contact with metallic tools introduces an occupational allergen exposure. However, data on nickel and cobalt release from commonly handled cutting tools remain limited. Objectives: To estimate nickel and cobalt spot‐test positivity in hairdressing tools used in Danish hair salons. Materials and Methods: In this cross‐sectional field study, 58 voluntarily participating Danish salons were visited from 1 March to 30 June 2026. Scissors, hair clippers and razors were each tested once for nickel with dimethylglyoxime and for cobalt with nitroso‐R salt colorimetric spot tests. Results: Among 266 tools (167 scissors, 95 hair clippers and 4 razors), 37 (13.9%) were positive to nickel and 18 (6.8%) to cobalt. Nickel positivity was 15.6% in scissors and 10.5% in hair clippers; cobalt positivity was 6.6% and 6.3%, respectively. At least one positive tool occurred in 22/58 (37.9%) salons for nickel and 12/58 (20.7%) for cobalt. Conclusions: Nickel and cobalt release from commonly used hairdressing tools is a prevalent occupational hazard. These findings underscore the necessity of proactive preventive strategies, such as careful material selection and stricter regulatory oversight.

Background: Gold contact allergy is common, but its clinical relevance is often uncertain. A previous study of low‐cost gold‐plated earrings found frequent nickel release and detectable gold release under cysteine‐modified artificial sweat. Objectives: To assess surface composition and release of gold, nickel and copper from jeweller‐purchased earrings marketed as 10K or 14K gold. Methods: Five pairs of earrings were examined by scanning electron microscopy ( SEM ) with energy‐dispersive spectroscopy ( EDS ). Release testing used cysteine‐modified artificial sweat at pH 8.0 ± 0.2 and 30°C for 168 h. Metals were quantified by inductively coupled plasma mass spectrometry ( ICP ‐ MS ). Results: Surfaces consisted mainly of gold, copper, silver and zinc. EDS ‐detected gold ranged from 40 to 63 wt%, and nickel from 0.085 to 0.20 wt%. Nickel release was < LOD in all pairs. Gold release was detected from all pairs (median 0.057 μg/cm ² /week, range: 0.016–0.15). Copper release exceeded gold release in all samples (median: 0.53 μg/cm ² /week, range: 0.36–2.2). Conclusion: Jeweller‐purchased 10K / 14K gold earrings released measurable gold but not detectable nickel under cysteine‐modified artificial sweat conditions. Gold release provides a plausible exposure pathway but does not establish sensitization or elicitation risk.

Tape strip-based transcriptomics shows promise for precision medicine in inflammatory skin diseases, but methodological variation limits reproducibility and clinical use. This study investigates whether four or eight tape strips are sufficient for transcriptomic profiling across three inflammatory skin diseases. As part of the Danish cohort study BIOSKIN, patients with atopic dermatitis (AD), contact dermatitis (CD), psoriasis, and healthy controls (n = 8 per group) were enrolled. Two sets of eight consecutive tape strips were obtained from each participant from lesional skin (patients) or healthy skin (controls) and pooled for RNA sequencing as strips 1–8, 1–4, or 5–8. Despite low RNA yield, sequencing was successful across all disease groups. Gene detectability was consistent across tape strip strategies, with 78.1%, 73.1%, and 67.7% overlap across strips 1–4, 5–8, and 1–8 for psoriasis, AD, and CD, respectively. Principal component analysis distinguished patients with psoriasis and AD from healthy controls, and enrichment analysis captured biologically relevant pathways across all three disease groups. In psoriasis, tape strip transcriptomics captured a core psoriatic transcriptome consistent with paired biopsy data. Four tape strips were sufficient for RNA sequencing and detection of disease-relevant inflammatory responses, supporting their use in longitudinal cohort studies and split-sampling designs. Performance was most robust for psoriasis and AD; optimization may benefit CD given the challenges of palmar sampling.

The present guideline updates the initial ESCD patch testing guideline, summarizing all aspects of patch testing for the diagnosis of contact allergy in patients suspected of suffering, or having been suffering, from allergic contact dermatitis or other delayed‐type hypersensitivity skin and mucosal conditions. Sections with brief descriptions and discussions of different pertinent topics are followed by highlighted short practical recommendations, which have been consensualized in a Delphi process. Topics comprise, after an introduction with important definitions, materials, technique, modifications of epicutaneous testing, individual factors influencing the patch test outcome or necessitating special considerations, children, patients with occupational contact dermatitis and drug eruptions as special groups, patch testing of materials brought in by the patient, adverse effects of patch testing and the final evaluation and patient counselling based on this judgement. Finally, short reference is made to aspects of (continuing) medical education and to electronic collection of data for epidemiological surveillance.

Background: Contact allergy to methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) remains common in the EU despite regulation. Objectives: To assess the extent of use of MCI/MI and MI in cosmetic products on the Danish market, identify product categories involved and evaluate compliance of rinse‐off products with the 15 ppm limit. Materials and Methods: Products listing MCI/MI or MI were identified through Kemiluppen, a Danish database of marketed cosmetics. Thirty products (16 shampoos and 14 liquid soaps) were examined using liquid chromatography–tandem mass spectrometry: 25 labelled as containing MCI/MI or MI, 5 unlabelled. Results: In total, 257 cosmetic products containing MCI/MI or MI were identified, primarily shampoos (127), conditioners (98) and liquid soaps (8). Chemical analysis showed that 2 of 25 labelled products (8%) exceeded the 15 ppm limit, and 4 products did not meet the required 3:1 MCI/MI ratio. Conclusion: MCI/MI is used infrequently in cosmetic products. All, except two products complied with the limit in the regulation. Given the continued occurrence of contact allergy, this indicates that the limit (15 ppm) may be too high to be sufficiently protective. Further investigation into MCI/MI use in cosmetic products is warranted, alongside more proactive risk assessment and management strategies.

Contact allergy related to use of cosmetic products remains a considerable problem in the European Union population. The objectives of this study were to identify pitfalls in EU risk assessment methodologies and regulation(s) for cosmetic products and identify areas of potential improvements in future regulatory strategies. Two significant contact allergens, methylisothiazolinone and hydroxyisohexyl 3‐cyclohexene carboxaldehyde, were investigated as examples. Other contact allergens were used to provide additional context. Opinions from the European Commission's scientific committees and regulatory documents were analysed to identify methodologies, processes and results in terms of preventive effects. The analysis revealed key observations in five areas: risk assessment methodologies, prediction approaches, key data, regulatory process and linkages. The case study indicated that reliance on predictive sensitization data from healthy volunteers generated unrealistically high no/low effect levels, while epidemiological surveillance and patient‐based threshold data ultimately proved decisive, informing EU restrictions that led to declining sensitization rates. Read across approaches and chemical alert analyses show potential for earlier prevention, but their application has been inconsistent. Quantitative risk assessment remains limited by unresolved issues such as safety factors, aggregate exposure, and mixture effects. Strengthening transparency, integrating clinical evidence earlier, and improving regulatory coordination are essential to prevent future sensitization epidemics.

Background: Contact allergy to gold is frequently observed in patch testing, although with low clinical relevance. Nickel allergy, in contrast, is common, clinically relevant, and nickel release from jewellery remains a regulatory concern. Standardised artificial sweat tests show no detectable gold release from gold‐containing jewellery. Objectives: To assess surface composition and the release of nickel and gold from gold‐plated earrings under clinically relevant biochemical conditions. Methods: Ten pairs of low‐cost gold‐plated earrings were analysed by scanning electron microscopy (SEM) with energy‐dispersive spectroscopy (EDS) and X‐ray fluorescence. Metal release was assessed using a cysteine‐modified artificial sweat solution at 30°C for 168 h. Gold and nickel concentrations were quantified by inductively coupled plasma mass spectrometry. Results: Nickel release was detected in 10/10 earrings (median: 2.1 μg/cm ² , range: 0.00032–10.0) frequently exceeding the EU regulatory limit. Gold release was detected in 4/10 earrings (median: 0.00092 μg/cm ² , range: 0.00041–0.21). Gold was identified by cross‐sectional SEM/EDS in a subset of components (6/20) but was not detected by top‐down XRF analysis. Conclusion: Nickel release from gold‐plated earrings was widespread and often exceeded regulatory limits, indicating that gold plating does not reliably prevent nickel exposure. Gold release occurred in some earrings, but the clinical relevance remains uncertain.

Introduction: Leather is a recognised source of contact allergy to chromium (Cr). Cobalt (Co) has also been identified as a potential leather‐related allergen. Objectives: To assess the presence and release of Cr and Co in used leather items available on the Danish secondhand market. Methods: Thirty‐four used consumer leather items with expected direct skin contact during normal use were purchased from secondhand shops in Greater Copenhagen, Denmark. Cr and Co were measured using handheld X‐ray fluorescence ( XRF ). Cr( VI ) was measured according to International Organization for Standardization (ISO) standard 17 075‐1 following pre‐conditioning with ISO 10195. Extractable Co was analysed using ISO 17072‐1 and inductively coupled plasma mass spectrometry. Results: Cr( VI ) was detected in 12/34 (35.3%) items, with an average concentration of 1.77 mg/kg (range: 0.52–4.16). Co was detected in 7/34 (20.6%) items, with an average concentration of 0.63 mg/kg (range: 0.33–1.44). Shoes accounted for most items with higher Cr( VI ) concentrations. Conclusion: Used leather items may contain measurable levels of Cr(VI) and Co. Secondhand leather represents a relevant exposure scenario that should be considered in future exposure assessments and regulatory discussions.