Hand eczema (HE) is a common skin disease, diagnosed through clinical evaluation. However, the increasing need to deliver healthcare remotely, along with the demand for valid and reliable evaluations of HE in research, prompts exploration of the potential benefits of remote assessment. This study assessed the criterion validity and inter- and intra-rater reliability of patient-provided photographs to diagnose and assess the severity of HE. The presence and severity of HE were assessed by 1 of the 2 clinical raters. Following instructions, patients took 4 photographs of their hands. All photographs were assessed twice by the clinical raters and 2 additional raters. In total, 98 patients were included. The sensitivity, specificity, positive and negative predictive value were respectively 85.1%, 79.2%, 92.6%, and 63.3%. Kappa values of 0.35 and 0.66 were found for inter- and intra-rater reliability. The intraclass correlation coefficients based on the Hand Eczema Severity Index (HECSI) were > 0.90. Kappa values for the criterion validity and inter- and intra-rater reliability using the photographic guide were respectively 0.71, 0.58–0.77, and 0.77. The findings indicate that patient-provided photographs are valid and reliable for remote assessment of HE and could be of benefit in healthcare and research by reducing in-person visits and enabling continuous monitoring.

Background:General population-based studies addressing the association between occupational exposure to irritants and allergens and hand eczema (HE) are limited, or only focus on specific occupations using self-reported exposure data. Objectives:To assess the association between occupational exposure to irritants and allergens and moderate-to-very severe HE, by using the Occupational Asthma-specific job exposure matrix (OasJEM) within the Dutch general population, and to address the applicability of this approach. Methods:Within the Lifelines Cohort Study, participants with moderate-to-very severe HE at worst in the past year vs. no HE in lifetime were identified based on self-reports. The OasJEM was used to link occupations with occupational exposure to irritants and sensitizers, relying on expert-based classification. Results:In total, 56,978 (41.9%) participants were included. The multivariate binary logistic regression analyses showed associations between occupational exposure to irritants [Odds ratio (OR): 1.19 (95% CI: 1.06-1.33)], high molecular weight sensitizers [OR: 1.20 (95% CI: 1.06-1.36)], mites [OR: 1.41 (95% CI: 1.16-1.73)] and disinfectants and cleaning products [1.25 (95% CI: 1.11-1.42)], and moderate-to-very severe HE. Conclusions:While associations between several irritants and allergens and HE were found by applying the OasJEM, which may provide insights into occupational exposure patterns and highlight the general relevance of occupational exposure in relation to HE and its prevention, several methodological and conceptual challenges must be acknowledged. A JEM not specifically designed for HE, like the OasJEM, may not fully capture the complex interplay between occupational exposure and HE, particularly in reflecting direct skin contact, the primary exposure route relevant for HE. However, in the absence of widely available and reliable HE-specific exposure assessment tools, the use of non-HE-specific JEMs may be considered a pragmatic alternative, while acknowledging certain limitations. Future studies should focus on task-based and HE-specific exposure data, providing more accurate insights into occupational exposure and HE.

BACKGROUND:Atopic dermatitis (AD) has characteristics of a systemic disease due to underlying systemic inflammation, which is supported by reports of various comorbidities. OBJECTIVES:To examine the associations between AD and (nonatopic) multimorbidity in a population-based cohort from the northern Netherlands and to identify differences in multimorbidity patterns between participants with multimorbidity and no AD. METHODS:We assessed the lifetime prevalence of 52 diseases, from 15 domains, combining data from questionnaires, medication records and clinical assessments within the Lifelines Cohort. Lifetime AD was self-reported, physician-diagnosed and disease severity based on the Patient-Oriented Eczema Measure. Multimorbidity was defined as the lifetime presence of at least two diseases, while nonatopic multimorbidity excluded asthma, rhinitis and food allergy. A composite morbidity score (cMS) indicated the degree of multimorbidity. We analysed associations of AD and AD severity with multimorbidity and cMS using binary and multinomial logistic regression, adjusting for age and sex, and additionally adjusting for socioeconomic and lifestyle factors. Patterns of nonatopic multimorbidity based on disease domains were explored using latent class analysis, stratified by AD presence. RESULTS:Of 37 193 participants, 3242 (8.7%) had AD. The odds for nonatopic multimorbidity were 1.47-fold higher in participants with AD, particularly for those with moderate-to-severe disease (adjusted odds ratio 1.74 vs. 1.41 for mild disease). The association strengthened with higher degrees of nonatopic multimorbidity, reaching 2.09-fold for ≥ 5 diseases. When considering atopic diseases in the definition of multimorbidity and the cMS, the associations with AD were even stronger. Further adjustments for socioeconomic and lifestyle factors were corroborative. We identified five distinct multimorbidity classes among individuals with and without AD, with two differing across the groups. One class, characterized by the orofacial domain, was only present among those with AD, while another class - resembling the metabolic syndrome - had more of a respiratory contribution to AD with further differences regarding cardiometabolic involvement. CONCLUSIONS:Participants with AD, especially moderate-to-severe disease, are more likely to experience (nonatopic) multimorbidity and showed unique patterns of nonatopic multimorbidity with regard to orofacial and cardiometabolic diseases. Our findings highlight the importance of promoting awareness for interdisciplinary approaches to managing patients with AD. An author video to accompany this article is available online.

ABSTRACT Background Allergens are periodically added to the European Baseline Series (EBS) to audit their value in consecutive patch testing. Objectives To present results of audit allergens tested in consecutive patients in 54 departments in 13 European countries during 2021 and 2022. Methods Anonymized or pseudonymized individual data, and partly aggregated data on patch test rest results and their clinical relevance were prospectively collected and centrally pooled and analyzed. Results In 2021 and 2022, 18 832 patients were patch tested with the EBS, and 2860 with the TRUE Test baseline series (supplemented with some missing EBS allergens). Of these patients, 17 359 were additionally tested with one or more of the 19 audit allergen preparations examined. Apart from the terpene hydroperoxides (OOH) which yielded the highest numbers of positive patch test reactions (linalool‐OOH 1% pet.: 7.65 (7.09%–8.23%) [95% CI] and limonene‐OOH 0.3% pet. 6.78 (6.26%–7.32%)), positive reactions were most often seen to benzisothiazolinone (3.71 (3.3%–4.15%)), sodium metabisulfite (3.49 (3.14%–3.88%)), Evernia furfuracea (tree moss, 1.79 (1.4%–2.26%)), and decyl and lauryl glucoside, at 1.49 (1.25%–1.76%) and 1.26 (1.05%–1.51%), respectively. The other allergens yielded around 1% or fewer positive patch test reactions. Clinical relevance varied, with Evernia furfuracea , 2‐bromo‐2‐nitropropane‐1,3‐diol and terpene hydroperoxides considered relevant in more than 2/3 cases, while for other frequent sensitizers benzisothiazolinone and sodium metabisulfite, relevance could be confirmed in half of the cases or less often. Conclusions The current results, along with other published data, will serve to inform decisions concerning possible revision of the EBS, considering frequency of positive reactions, their clinical relevance and the overall reaction profile of each of the allergens.

BACKGROUND:Allergens are periodically added to the European Baseline Series (EBS) to audit their value in consecutive patch testing. OBJECTIVES:To present results of audit allergens tested in consecutive patients in 54 departments in 13 European countries during 2021 and 2022. METHODS:Anonymized or pseudonymized individual data, and partly aggregated data on patch test rest results and their clinical relevance were prospectively collected and centrally pooled and analyzed. RESULTS:In 2021 and 2022, 18 832 patients were patch tested with the EBS, and 2860 with the TRUE Test baseline series (supplemented with some missing EBS allergens). Of these patients, 17 359 were additionally tested with one or more of the 19 audit allergen preparations examined. Apart from the terpene hydroperoxides (OOH) which yielded the highest numbers of positive patch test reactions (linalool-OOH 1% pet.: 7.65 (7.09%-8.23%) [95% CI] and limonene-OOH 0.3% pet. 6.78 (6.26%-7.32%)), positive reactions were most often seen to benzisothiazolinone (3.71 (3.3%-4.15%)), sodium metabisulfite (3.49 (3.14%-3.88%)), Evernia furfuracea (tree moss, 1.79 (1.4%-2.26%)), and decyl and lauryl glucoside, at 1.49 (1.25%-1.76%) and 1.26 (1.05%-1.51%), respectively. The other allergens yielded around 1% or fewer positive patch test reactions. Clinical relevance varied, with Evernia furfuracea, 2-bromo-2-nitropropane-1,3-diol and terpene hydroperoxides considered relevant in more than 2/3 cases, while for other frequent sensitizers benzisothiazolinone and sodium metabisulfite, relevance could be confirmed in half of the cases or less often. CONCLUSIONS:The current results, along with other published data, will serve to inform decisions concerning possible revision of the EBS, considering frequency of positive reactions, their clinical relevance and the overall reaction profile of each of the allergens.

ABSTRACT Background Patch test results obtained with the European Baseline Series (EBS) in its current version serve both contact allergy surveillance and (re‐)assessing the diagnostic value of EBS allergens. Objectives To present results of current EBS patch testing, obtained in 59 departments in 14 European countries during 2021 and 2022. Methods Anonymised or pseudonymised individual data, and partly aggregated results, on demographic/clinical characteristics and patch test results with the EBS were prospectively collected, centrally pooled, and retrospectively analysed. Results In 2021 and 2022, 18 832 patients were patch tested with the EBS. Sensitization to nickel remained most common (18.85 (18.29–19.43)% positivity (95% confidence interval)). Fragrance mix I and Myroxylon pereirae resin yielded very similar results with 6.39 (6.04–6.76)% and 6.5 (6.15–6.87)% positivity, respectively. Concerning preservatives, methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) 0.02% aq. yielded 5.52 (5.11–5.96)% and MI 0.2% aq. yielded 5.28 (4.94–5.64)% positives. Testing formaldehyde 2% aq. identified almost one percentage point more positive reactions than 1% aq. (2.05 (1.81–2.32)% vs. 1.22 (0.99–1.48)). Positive reactions to the recently added allergens were most frequently seen to propolis (5.47 (5.12–5.84)%) and 2‐hydroxyethyl methacrylate (3.63 (3.32–3.96)%). Conclusions Compared to the previous reporting period, surveillance results with the EBS were mostly stable. The results regarding Quaternium 15 (0.4 (0.29–0.53)% positives) justified its exclusion from the 2023 EBS version.

BACKGROUND:Patch test results obtained with the European Baseline Series (EBS) in its current version serve both contact allergy surveillance and (re-)assessing the diagnostic value of EBS allergens. OBJECTIVES:To present results of current EBS patch testing, obtained in 59 departments in 14 European countries during 2021 and 2022. METHODS:Anonymised or pseudonymised individual data, and partly aggregated results, on demographic/clinical characteristics and patch test results with the EBS were prospectively collected, centrally pooled, and retrospectively analysed. RESULTS:In 2021 and 2022, 18 832 patients were patch tested with the EBS. Sensitization to nickel remained most common (18.85 (18.29-19.43)% positivity (95% confidence interval)). Fragrance mix I and Myroxylon pereirae resin yielded very similar results with 6.39 (6.04-6.76)% and 6.5 (6.15-6.87)% positivity, respectively. Concerning preservatives, methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) 0.02% aq. yielded 5.52 (5.11-5.96)% and MI 0.2% aq. yielded 5.28 (4.94-5.64)% positives. Testing formaldehyde 2% aq. identified almost one percentage point more positive reactions than 1% aq. (2.05 (1.81-2.32)% vs. 1.22 (0.99-1.48)). Positive reactions to the recently added allergens were most frequently seen to propolis (5.47 (5.12-5.84)%) and 2-hydroxyethyl methacrylate (3.63 (3.32-3.96)%). CONCLUSIONS:Compared to the previous reporting period, surveillance results with the EBS were mostly stable. The results regarding Quaternium 15 (0.4 (0.29-0.53)% positives) justified its exclusion from the 2023 EBS version.

BACKGROUND:Dupilumab and tralokinumab for atopic dermatitis (AD) target the type 2 axis through different mechanisms of action, which may lead to variation in effectiveness and safety. Head-to-head trials, however, are lacking. OBJECTIVES:To compare the real-world effectiveness and safety of dupilumab and tralokinumab in AD. METHODS:This prospective cohort study enrolled biologic-/Janus kinase inhibitor-naïve AD patients (≥12 years) from the BioDay registry who initiated dupilumab or tralokinumab between November 2021 and September 2024. Visits were scheduled at baseline, 4 weeks and every 3 months up to 52 weeks. Effectiveness outcomes included Eczema Area and Severity Index (EASI), weekly mean pruritus Numeric Rating Scale (NRS), treat-to-target thresholds (EASI ≤ 7; NRS-pruritus ≤ 4, with patients discontinuing treatment considered non-responders) and drug survival. Adverse events (AEs) were assessed at each visit. Inverse probability of treatment weighting (IPTW) was used to balance treatment groups. RESULTS:In total, 750 patients were included (643 dupilumab; 107 tralokinumab). After IPTW, baseline characteristics were well balanced. During follow-up, dupilumab patients had lower EASI scores than tralokinumab patients, although differences were not consistently statistically significant (p = 0.10). NRS-pruritus scores were significantly lower with dupilumab at all visits (p < 0.0001), mean differences did not exceed the 2-point clinical relevance threshold. The probability of achieving EASI ≤ 7 and NRS-pruritus ≤ 4 was higher with dupilumab (both p < 0.0001), with risk differences of 34.7% and 40.2% at 52 weeks, respectively. After 52 weeks, dupilumab drug survival was 92.6% vs. 70.6% for tralokinumab. Ocular surface disease incidence was similar (HR 1.0, 95% CI 0.6-1.6, p = 0.94) between treatments, leading to discontinuation of dupilumab in n = 23 (3.4/100 PY) and tralokinumab in n = 5 (5.4/100 PY). CONCLUSIONS:In this real-world comparison, dupilumab provided superior effectiveness compared with tralokinumab. In responders continuing treatment, EASI and NRS-pruritus differences were small. More substantial differences were observed when treatment targets EASI ≤ 7 and NRS-pruritus ≤ 4, and discontinuation rates were taken into account.

Background:The hygiene hypothesis suggests that reduced microbial exposure may contribute to the development of atopic diseases, whereas higher exposure may exacerbate symptoms and promote disease progression. Objectives:To investigate the association between multiple childhood environmental exposures and atopic multimorbidity, defined as atopic dermatitis (AD) accompanied by at least two other atopic comorbidities, including asthma, food allergy (FA) and allergic rhinitis (AR). Methods:Data on self-reported, physician-diagnosed lifetime AD were collected in 2020 through a digital questionnaire within the Lifelines Cohort Study, an ongoing population-based study including 167 729 residents of the northern Netherlands. Adults retrospectively reported childhood environmental exposures, including birthweight, gestational age, delivery mode, breastfeeding, tobacco smoke exposure (maternal or childhood), cat or dog ownership before the age of 16 years (ever owned, type and age at ownership) and living conditions. All exposure data, along with data on asthma, AR and FA, were collected between 2006 and 2013. Associations between environmental exposures and atopic multimorbidity (vs. no atopic disease) were assessed using logistic regression, adjusted for age, sex, socioeconomic status, parental history of asthma and sibling status. Results:Among 28 791 included participants, 27 939 (97.0%) reported no atopic diseases, while 852 (3.0%) reported atopic multimorbidity. Compared with participants without atopic diseases, caesarean section delivery was positively associated with atopic multimorbidity [odds ratio (OR) 2.55, 95% confidence interval (CI) 1.20-5.46], whereas pet ownership before the age of 16 years (OR 0.52, 95% CI 0.37-0.75), including ownership of dogs only (OR 0.59, 95% CI 0.37-0.94), cats only (OR 0.44, 95% CI 0.26-0.74) or both (OR 0.53, 95% CI 0.34-0.83), was negatively associated with atopic multimorbidity. Conclusions:Childhood pet ownership may be protective against atopic multimorbidity, whereas caesarean section delivery may be associated with a higher likelihood of atopic multimorbidity, providing insights into potential preventive strategies.

BACKGROUND:Delgocitinib cream is the only topical treatment that has been specifically developed and approved for moderate to severe Chronic Hand Eczema (CHE). OBJECTIVE:The objective of this trial was to evaluate the long-term safety and efficacy of delgocitinib cream 20 mg/g as needed for 36 weeks in adults with CHE. METHODS:In phase 3 open-label DELTA 3 (NCT04949841), patients who completed the 16-week treatment period in the DELTA 1 and 2 trials were treated on an as-needed basis with twice-daily delgocitinib cream for 36 weeks (n= 801). Patients with Investigator's Global Assessment for CHE (IGA-CHE) ≥2 received treatment until IGA-CHE ≤1 was achieved. The primary endpoint was the number of treatment-emergent adverse events. Key secondary endpoints were IGA-CHE 0/1 and ≥75%/≥90% improvement in Hand Eczema Severity Index (HECSI-75/90) scores. RESULTS:Delgocitinib was well-tolerated (n= 801; R = 231.1; patient years of observation = 535.7), with most frequent adverse events being COVID-19 and nasopharyngitis. DELTA 3 baseline IGA-CHE 0/1 (24.6%) and HECSI-75/HECSI-90 (51.8%/31.8%) were maintained to week 36 (30.0% and 58.6%/36.6%, respectively) among delgocitinib-treated patients in the parent trials. Among those previously treated with cream vehicle, corresponding response rates improved from DELTA 3 baseline (9.1% and 23.7%/12.0%, respectively) to week 36 (29.5% and 51.5%/35.7%). LIMITATIONS:Open-label trial. CONCLUSION:Delgocitinib cream treatment was well-tolerated and efficacious in maintaining disease control in patients with CHE for up to 52 weeks.

Abstract In the monotherapy phase 3 trial (ECZTRA 6, NCT03526861) in adolescents with moderate-to-severe atopic dermatitis (AD) treated with tralokinumab, IGA of clear/almost clear skin (IGA 0/1) at week 16 was a primary endpoint. IGA 0/1 can be a high standard to achieve for patients with moderate-to-severe AD and may not fully reflect achievement of other clinically meaningful parameters, such as improvement in signs, symptoms and/or quality-of-life (QoL). To assess the impact of tralokinumab (150 or 300 mg) vs. placebo on other clinically meaningful parameters at week 16 in the subset of patients who did not achieve IGA 0/1 at week 16 and/or used rescue medication. Adolescents (12–17 years) were randomized to subcutaneous tralokinumab 150 or 300 mg, or placebo, every 2 weeks. Patients who did not achieve IGA 0/1 at week 16 and/or utilized rescue therapy were included in this post-hoc analysis. Non-responder imputation was used for patients who utilized rescue therapy or had missing data. Clinically meaningful responses were defined as EASI-50, ≥ 3-point improvement in pruritus NRS, or ≥6-point improvement in CDLQI. At week 16, 78.6% and 82.5% of tralokinumab-treated patients (150 mg/300 mg) vs. 95.7% (placebo) exhibited IGA > 1 and/or used rescue therapy. 36.4% (150 mg) and 52.5% (300 mg) of patients with IGA > 1 in the tralokinumab arms, compared to 21.1% (placebo), achieved clinically meaningful responses in at least one measure: EASI-50, pruritus NRS, or CDLQI. Greater proportions of tralokinumab-treated patients (150/300 mg vs. placebo) achieved EASI-50 (31.2%/41.3% vs. 10.0%) and ≥3-point improvement in pruritus NRS (21.6%/22.8% vs. 8.0%). A greater proportion of tralokinumab 300 mg patients vs. placebo (35.2% vs. 15.0%) achieved ≥6-point improvement in CDLQI. Many tralokinumab-treated adolescents who did not achieve IGA 0/1 at week 16 and/or used rescue therapy still achieved clinically meaningful improvements in AD signs, symptoms, and/or QoL.

The Atopic Dermatitis Control Tool (ADCT) has not been validated in the Dutch population, and comparisons with the Recap of atopic eczema (RECAP) questionnaire are still lacking. This prospective study was conducted at a Dutch tertiary hospital between June 2021 and December 2022, to assess measurement properties of the Dutch ADCT in adults with atopic dermatitis (AD) and compare it with RECAP. Participants completed the ADCT, RECAP, and reference instruments including Patient’s Global Assessment (PtGA), Patient-Oriented Eczema Measure (POEM), Dermatology Life Quality Index (DLQI), quality-of-life questionnaire of the EuroQol Group (EQ-5D-5L), Numeric Rating Scale (NRS) peak itch/sleep disturbance, Skindex-29, and Global Rating of Change (GRC), at baseline, 1–3 days, and 4–12 weeks. Construct validity was assessed through a priori hypotheses, whilst reliability was evaluated with standard error of measurement (SEMagreement) and intraclass correlation coefficient (ICCagreement). Interpretability was examined using anchor-based approaches. In total, 196 adults with AD were included. Among a priori hypotheses, 82% (single-score validity) and 59% (responsiveness) were confirmed. The SEMagreement was 1.15, and the ICCagreement was 0.983. The final bandings for the ADCT were established, with a binary cutoff of ≥ 6 indicating uncontrolled AD. The smallest detectable change (SDC) was 3.2, and the minimally important change (MIC) value from predictive modelling was 2.9. Furthermore, the ADCT exhibited high correlations with RECAP at all levels (most correlations being above 0.80). These results demonstrated the Dutch ADCT as a valid, reliable, and responsive tool, and have important clinical implications.

BACKGROUND:Contact allergy is common in children, but no paediatric baseline series (pEBS) exists in Europe, despite recommendations in several countries. OBJECTIVES:To collect and compare patch testing data from European centres to propose a common pEBS, possibly adapted by age group. MATERIALS AND METHODS:Data from 13 centres in 12 European countries were aggregated, covering 1816 children (1099 girls, 60.5%), aged 0-16 years, tested with the adult EBS (aEBS) and other frequent allergens between 2018 and 2022. Allergen selection followed adult criteria, with a stricter cut-off for inclusion, requiring at least 1% positive reactions (lower 95% CI) in children. RESULTS:A total of 17 allergens from the aEBS caused positive reactions in ≥ 1% of children (lower 95% CI). Common allergens included metals, fragrances, and preservatives. Tixocortol-21-pivalate was included despite its lower frequency due to its difficult-to-suspect nature. Additional frequent allergens were hydroperoxides of limonene and linalool, Amerchol L-101, and sorbitan sesquioleate. In total, 18 allergens were identified as potentially qualifying for a pEBS, with a further 7 as recommended additions. CONCLUSION:Results from patch testing children across europe highlight a common set of frequent allergens, which should be considered for a pEBS.

Investigator’s Global Assessment (IGA) of clear/almost clear (0/1) skin is a high standard to achieve after 16 weeks of treatment for patients with moderate-to-severe atopic dermatitis (AD) and does not capture clinically meaningful responses in other patient domains, such as improvement in itch and/or quality of life. To better evaluate the effect of tralokinumab in adolescents, we assessed the clinically meaningful impact of tralokinumab versus placebo in patients who did not meet IGA 0/1 at week 16 without rescue medication in ECZTRA 6. These post hoc analyses included adolescents from the ECZTRA 6 (NCT03526861) phase 3 trial who did not achieve IGA 0/1 at week 16 without rescue medication (referred to as IGA >1). Clinically meaningful responses were defined as either ≥50 Atopic dermatitis is a common and chronic skin disease where patients experience severe itch and skin lesions. Atopic dermatitis can negatively affect patient quality of life, especially for adolescents, whose self-esteem and body image can greatly influence their perception of social interactions. Tralokinumab is a medication that is approved for treating moderate-to-severe atopic dermatitis in patients aged 12 years and up. Clinical trials for atopic dermatitis therapies often define treatment success using a single clinician-measured metric of clear or almost clear skin at week 16. Patients who do not achieve this are considered a treatment failure. However, this limited definition of treatment success does not reflect the complete patient experience, especially for those with lesions across much of their skin. Here, we used data from the ECZTRA 6 phase 3 clinical trial, funded by LEO Pharma A/S, to analyze if adolescent patients treated with tralokinumab, who did not meet the trial definition for treatment success, still showed meaningful improvement in atopic dermatitis symptoms. Overall, in this group, a larger percentage of patients treated with tralokinumab, compared with those who did not receive active drug (i.e., placebo), showed improvements in the severity of skin lesions, itch, and patient quality of life at week 16. Additionally, patients continued to improve with ongoing tralokinumab treatment beyond week 16. Our results suggest using several outcomes directly reported by patients, in addition to clinician-measured metrics, can better inform tralokinumab treatment management in adolescents with moderate-to-severe atopic dermatitis

BACKGROUND:Sociodemographic and lifestyle factors may be related to the use of cosmetic procedures with potential adverse skin effects, such as hair dye use. OBJECTIVES:To investigate the association of several sociodemographic and lifestyle factors with (adverse skin reactions to) hair dye use in the Dutch general population. METHODS:This cross-sectional study used questionnaire-derived data from the population-based Lifelines cohort regarding lifetime hair dye use and adverse skin reactions (n = 70 987). Logistic regression analyses investigated associations of sociodemographic factors (ethnicity, hair colour, marital status, educational attainment, income, neighbourhood socioeconomic status) and lifestyle factors (smoking, alcohol consumption, and body mass index [BMI]) with adverse skin reactions to hair dye use. RESULTS:Hair dye use was significantly positively associated with having dark blonde or brown hair colour, lower educational attainment, smoking, daily alcohol consumption and higher BMI. Hair dye use was significantly negatively associated with having red or auburn hair colour. Furthermore, adverse skin reactions to hair dye were significantly positively associated with higher BMI. CONCLUSIONS:Our findings highlight several positive associations between sociodemographic and lifestyle factors and both hair dye use and its adverse skin reactions. Notably, elevated BMI was consistently positively associated with both hair dye use and adverse skin reactions.