A genome-wide association study of hand eczema identifies locus 20q13.33 and reveals genetic overlap with atopic dermatitis.

BACKGROUND: Twin studies revealed that genetic effects play a role in hand eczema (HE), but the responsible genetic factors are unknown. OBJECTIVES: To identify and characterise genetic loci associated with HE and to provide insight into the genetic overlap between HE and atopic dermatitis (AD). METHODS: We used questionnaire-derived and genotype data from the European population-based Lifelines cohort and biobank. We performed a discovery genome-wide association study (GWAS) of HE (2879 cases and 16 249 controls) and of AD (1706 cases and 17 190 controls). We replicated our findings in an independent Lifelines sample for HE (1188 cases and 6431 controls) and AD (757 cases and 6747 controls). We conducted several post-GWAS analyses and performed genetic correlation analyses between our HE results and independent AD data. RESULTS: The two-step GWAS of HE, regardless of adjusting for AD, identified one independent locus 20q13.33, likely driven by a number of causal single-nucleotide polymorphisms. For the AD GWAS, we replicated a known stop-gained rs61816761 at locus 1q21.3 (FLG, FLGAS1). We found a strong genetic correlation (p < 0.01) between HE and AD (rg = 0.65), regardless of adjusting for AD (rg = 0.63). CONCLUSIONS: Locus 20q13.33 is associated with HE, and there is a large genetic overlap between HE and AD.

New positive patch test reactions on day 7-The additional value of the day 7 patch test reading.

BACKGROUND: Not performing a day (D) 7 patch test reading might result in positive patch test reactions being missed. OBJECTIVES: To investigate the added value of the D7 patch test reading for individual allergens, and to identify patient characteristics and allergen groups associated with new positive D7 reactions. METHODS: Data from patients patch tested between 2008 and 2018 with the extended European baseline series were analysed. Patch test readings were performed on D3 and D7. Positive reactions were categorized into positive on D3 or new positive on D7. RESULTS: A total of 3292 patients were consecutively patch tested with at least 43 allergens of the TRUE Test panels 1 and 2 supplemented with investigator-loaded allergens. In total, 447 (13.6%) patients showed new positive D7 reactions. In univariable regression analysis, age between 18 and 30 years showed a negative association with new positive D7 reactions. Significantly more D7 positive reactions were seen for topicals (odds ratio [OR] 2.60, 95% confidence interval [CI]: 1.92-3.51) and corticosteroids (OR 1.87, 95%CI: 1.09-3.21). No associations were found between sex, atopic dermatitis and occupational dermatitis and a new positive D7 reaction. CONCLUSION: A D7 reading to identify new positive patch test reactions is of added value, especially for topicals and corticosteroids.

Contact sensitization to hydroperoxides of limonene and linalool: Results of consecutive patch testing and clinical relevance.

BACKGROUND: Hydroperoxides of limonene and linalool are potent sensitizers. OBJECTIVES: To investigate the prevalence of contact allergy to both hydroperoxides of limonene and hydroperoxides of linalool, to report clinical relevance, and to investigate patient demographics. METHODS: A total of 821 patients (35.6% male, mean age 42.4 years ± 17.8 years) were consecutively patch tested with our departmental baseline series and our fragrance series, including hydroperoxides of limonene 0.3% pet. and hydroperoxides of linalool 1.0% pet. The clinical relevance was assessed for all positive reactions. RESULTS: Positive patch test reactions to hydroperoxides of limonene and to hydroperoxides of linalool were observed in 77 patients (9.4%, 95% confidence interval [CI]: 7.4%-11.4%) and in 96 patients (11.7%, 95%CI: 9.5%-13.9%), respectively; 38 of these patients (4.6%, 95%CI: 3.2%-6.0%) reacted to both. Most reactions were considered to be possibly or probably clinically relevant (66.3% and 68.8%, respectively), and a small proportion were deemed to be of certain clinical relevance (18.2% and 19.8%, respectively). CONCLUSION: As compared with previous studies, high numbers of positive reactions to both hydroperoxides of limonene and hydroperoxides of linalool were observed, the majority of which were clinically relevant, supporting their inclusion in the European baseline series.

Cross-elicitation responses to 2-methoxymethyl-p-phenylenediamine in p-phenylenediamine-allergic individuals: Results from open use testing and diagnostic patch testing.

BACKGROUND: Allergic contact dermatitis caused by p-phenylenediamine (PPD) is a health concern for hair dye users. Because of its lower sensitization potency, the PPD derivative 2-methoxymethyl-p-phenylenediamine (ME-PPD) has been developed as an alternative hair dye for primary prevention. However, cross-elicitation responses can occur in PPD-allergic subjects. OBJECTIVES: To compare cross-elicitation responses to ME-PPD in open use and diagnostic patch testing of PPD-allergic subjects with hair dye-related allergic contact dermatitis. METHODS: Reactions to ME-PPD were investigated in 25 PPD-allergic subjects by performing (1) 45-minute open use testing with a hair dye containing 2.0% of either ME-PPD or PPD, and (2) patch testing with increasing ME-PPD concentrations (0.1%-2.0% pet.). RESULTS: Of the 25 PPD-allergic subjects, 21 (84%) reacted to open use testing with a hair dye containing 2.0% PPD, and testing with 2.0% ME-PPD led to cross-elicitation in 12 (48%). When patch tested with increasing ME-PPD concentrations, 13 (52%) cross-reacted at 0.1% (lowest dose) and 21 (84%) at 2.0% (highest dose), indicating decreased reactivity as compared with published PPD dose-response data. CONCLUSION: In line with the decreased cross-reactivity of ME-PPD in hair dye open use testing, PPD-allergic subjects show an attenuated cross-elicitation dose response to ME-PPD in patch testing.

Interventions for preventing occupational irritant hand dermatitis.

BACKGROUND: Occupational irritant hand dermatitis (OIHD) causes significant functional impairment, disruption of work, and discomfort in the working population. Different preventive measures such as protective gloves, barrier creams and moisturisers can be used, but it is not clear how effective these are. This is an update of a Cochrane review which was previously published in 2010. OBJECTIVES: To assess the effects of primary preventive interventions and strategies (physical and behavioural) for preventing OIHD in healthy people (who have no hand dermatitis) who work in occupations where the skin is at risk of damage due to contact with water, detergents, chemicals or other irritants, or from wearing gloves. SEARCH METHODS: We updated our searches of the following databases to January 2018: the Cochrane Skin Specialised Register, CENTRAL, MEDLlNE, and Embase. We also searched five trials registers and checked the bibliographies of included studies for further references to relevant trials. We handsearched two sets of conference proceedings. SELECTION CRITERIA: We included parallel and cross-over randomised controlled trials (RCTs) which examined the effectiveness of barrier creams, moisturisers, gloves, or educational interventions compared to no intervention for the primary prevention of OIHD under field conditions. DATA COLLECTION AND ANALYSIS: We used the standard methodological procedures expected by Cochrane. The primary outcomes were signs and symptoms of OIHD developed during the trials, and the frequency of treatment discontinuation due to adverse effects. MAIN RESULTS: We included nine RCTs involving 2888 participants without occupational irritant hand dermatitis (OIHD) at baseline. Six studies, including 1533 participants, investigated the effects of barrier creams, moisturisers, or both. Three studies, including 1355 participants, assessed the effectiveness of skin protection education on the prevention of OIHD. No studies were eligible that investigated the effects of protective gloves. Among each type of intervention, there was heterogeneity concerning the criteria for assessing signs and symptoms of OIHD, the products, and the occupations. Selection bias, performance bias, and reporting bias were generally unclear across all studies. The risk of detection bias was low in five studies and high in one study. The risk of other biases was low in four studies and high in two studies.The eligible trials involved a variety of participants, including: metal workers exposed to cutting fluids, dye and print factory workers, gut cleaners in swine slaughterhouses, cleaners and kitchen workers, nurse apprentices, hospital employees handling irritants, and hairdressing apprentices. All studies were undertaken at the respective work places. Study duration ranged from four weeks to three years. The participants' ages ranged from 16 to 67 years.Meta-analyses for barrier creams, moisturisers, a combination of both barrier creams and moisturisers, or skin protection education showed imprecise effects favouring the intervention. Twenty-nine per cent of participants who applied barrier creams developed signs of OIHD, compared to 33% of the controls, so the risk may be slightly reduced with this measure (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.72 to 1.06; 999 participants; 4 studies; low-quality evidence). However, this risk reduction may not be clinically important. There may be a clinically important protective effect with the use of moisturisers: in the intervention groups, 13% of participants developed symptoms of OIHD compared to 19% of the controls (RR 0.71, 95% CI 0.46 to 1.09; 507 participants; 3 studies; low-quality evidence). Likewise, there may be a clinically important protective effect from using a combination of barrier creams and moisturisers: 8% of participants in the intervention group developed signs of OIHD, compared to 13% of the controls (RR 0.68, 95% CI 0.33 to 1.42; 474 participants; 2 studies; low-quality evidence). We are uncertain whether skin protection education reduces the risk of developing signs of OIHD (RR 0.76, 95% CI 0.54 to 1.08; 1355 participants; 3 studies; very low-quality evidence). Twenty-one per cent of participants who received skin protection education developed signs of OIHD, compared to 28% of the controls.None of the studies addressed the frequency of treatment discontinuation due to adverse effects of the products directly. However, in three studies of barrier creams, the reasons for withdrawal from the studies were unrelated to adverse effects. Likewise, in one study of moisturisers plus barrier creams, and in one study of skin protection education, reasons for dropout were unrelated to adverse effects. The remaining studies (one to two in each comparison) reported dropouts without stating how many of them may have been due to adverse reactions to the interventions. We judged the quality of this evidence as moderate, due to the indirectness of the results. The investigated interventions to prevent OIHD probably cause few or no serious adverse effects. AUTHORS' CONCLUSIONS: Moisturisers used alone or in combination with barrier creams may result in a clinically important protective effect, either in the long- or short-term, for the primary prevention of OIHD. Barrier creams alone may have slight protective effect, but this does not appear to be clinically important. The results for all of these comparisons were imprecise, and the low quality of the evidence means that our confidence in the effect estimates is limited. For skin protection education, the results varied substantially across the trials, the effect was imprecise, and the pooled risk reduction was not large enough to be clinically important. The very low quality of the evidence means that we are unsure as to whether skin protection education reduces the risk of developing OIHD. The interventions probably cause few or no serious adverse effects.We conclude that at present there is insufficient evidence to confidently assess the effectiveness of interventions used in the primary prevention of OIHD. This does not necessarily mean that current measures are ineffective. Even though the update of this review included larger studies of reasonable quality, there is still a need for trials which apply standardised measures for the detection of OIHD in order to determine the effectiveness of the different prevention strategies.

European Surveillance System on Contact Allergies (ESSCA): polysensitization, 2009-2014.

BACKGROUND: Polysensitization, defined as being allergic to three or more haptens from the European baseline series, is considered to reflect increased susceptibility to developing a contact allergy, and is likely to be associated with an impaired quality of life. OBJECTIVES: To evaluate the prevalences of polysensitization across Europe and to analyse factors associated with polysensitization. METHODS: Patch test data collected by the European Surveillance System on Contact Allergies (ESSCA; www.essca-dc.org) in consecutively patch tested patients from January 2009 to December 2014, comprising 11 countries and 57 departments, were retrospectively analysed. RESULTS: A total of 86 416 patients were available for analysis, showing a standardized prevalence of polysensitization of 7.02%, ranging from 12.7% (Austria) to 4.6% (Italy). Allergen pairs with the strongest association are reported for the total population, for South Europe, and for North/Central Europe. Overall, polysensitized patients showed a higher percentage of extreme (+++) positive patch test reactions than oligosensitized patients. Female sex, occupational dermatitis and age > 40 years were risk factors for polysensitization. CONCLUSIONS: The varying prevalences of polysensitization across Europe most likely reflect differences in patient characteristics and referral patterns between departments. Known risk factors for polysensitization are confirmed in a European dermatitis population.

Persistence of contact allergy: a retrospective analysis.

BACKGROUND: Studies have shown that not all positive patch test reactions are reproducible upon retesting, that is, persistent. Non-persistent reactions might represent initial false-positive reactions, meaning that patients might unnecessarily avoid allergens. OBJECTIVES: To investigate the occurrence of both persistent and non-persistent patch test reactions, to explore possible explanations, and to investigate whether allergen-specific differences exist. METHODS: A retrospective analysis was performed on patients who were patch tested at least twice between 1 January 1995 and 31 October 2016, with at least one positive patch test reaction to an allergen that had been retested. Both univariable and multivariable analyses were performed to investigate the influence of several factors on persistence. RESULTS: Of 274 retested positive reactions in 119 patients, 183 (66.8%) reactions remained positive. The strongest predictor for non-persistence in both univariable and multivariable analyses was strength of the first patch test, with weak positive reactions being significantly less persistent. Regarding allergen groups, metals and fragrances were less persistent than other allergens. CONCLUSION: Weak positive reactions have a low persistence rate, and the dermatologist should be conservative in advising the patient on avoidance of these allergens, especially if clinical relevance is uncertain.

Immunology and genetics of tumour necrosis factor in allergic contact dermatitis.

During the sensitization phase of allergic contact dermatitis, the proinflammatory cytokine tumour necrosis factor (TNF) plays an important role by promoting epidermal Langerhans cell migration to draining lymph nodes. It also plays a role during the elicitation phase. The TNF gene (TNF) is located within the major histocompatibility complex region. Many single-nucleotide variants exist in the promoter region of TNF, and these may either increase or decrease mRNA transcription and therefore lead to higher or lower levels of TNF. The most extensively studied single-nucleotide variant of TNF is a base pair substitution in the promoter region at location -308 relative to the transcription start site (rs1800629, TNF -308G>A), which is believed to increase transcription and lead to higher TNF levels. The role of TNF in allergic contact dermatitis and the functionality of TNF -308G>A are reviewed in this article. The association between genetic variants and disease can be studied in a case-control design. Only a few case-control studies investigating the association between TNF -308G>A and allergic contact dermatitis have been published, with contradictory results. These are reviewed critically, and suggestions for future case-control studies on this topic are made.