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Summary: Background: Changing patterns of exposure lead to changes in the spectrum of contact allergy in the general population and in patients patch tested for suspected contact allergy. The main contact allergens (haptens) are assembled in the so‐called 'baseline series'. Objectives: To present the current spectrum of contact allergy to baseline series allergens, and its temporal development over the last 12 years, based on data collected by the 56 active departments of the trinational Information Network of Departments of Dermatology (IVDK). Methods: Patch‐test data, along with core demographic and clinical information, subdivided into 4‐year periods for all patients patch tested with the baseline series in the IVDK, were analysed descriptively. Moreover, log‐binomial regression analysis addressed temporal trends of specific contact allergies, adjusted for potentially confounding factors. Results: Among the 125 436 patients tested with the German baseline series, the most common allergens were nickel (14·7%), fragrance mix I (8·1%), Myroxylon pereirae resin (7·5%) and cobalt (5·2%), with no conclusive trend. The rise and fall of contact allergy to methylchloroisothiazolinone/methylisothiazolinone (MI), following (self‐) regulation in the European Union, reflected the MI contact allergy epidemic. Propolis showed a marked upward trend with a prevalence of 3·94% during the period 2015–2018. Conclusions: Decreases in sensitization prevalence likely reflect reduced exposure, with some lag, as seen with hydroxyisohexyl 3‐cyclohexene carboxaldehyde. If no (sufficient) decrease can be observed despite interventions, such as for nickel and chromium, affected subgroups should be identified and their causative exposures explored. Finally, increases such as that observed with propolis, certainly warrant targeted investigation of the exposures driving sensitization, and possibly intervention. What is already known about this topic? Contact allergy is prevalent in the general population.Surveillance based on clinical data offers timely information on trends concerning certain allergens or subgroups at risk. What does this study add? This analysis provides an update of the current contact allergy prevalence in Central Europe, including time trends.This study describes the demographic and clinical profile of patients tested from 2007 to 2018.This research identifies contact allergens that require (further) preventive efforts. Linked Comment:Schuttelaar. Br J Dermatol 2020; 183:800–801. What is already known about this topic? Contact allergy is prevalent in the general population.Surveillance based on clinical data offers timely information on trends concerning certain allergens or subgroups at risk. What does this study add? This analysis provides an update of the current contact allergy prevalence in Central Europe, including time trends.This study describes the demographic and clinical profile of patients tested from 2007 to 2018.This research identifies contact allergens that require (further) preventive efforts. Linked Comment:Schuttelaar. Br J Dermatol 2020; 183:800–801. Plain language summary available online Respond to this article [ABSTRACT FROM AUTHOR]

Summary: Background: Sodium lauryl sulfate (SLS) is the best‐studied detergent in irritant contact dermatitis. In atopic dermatitis, the two major pathophysiological abnormalities concern skin barrier function and regulation of cutaneous immune responses. The probability of atopic skin diathesis can be assessed by comprehensive analysis of patient history, as well as clinical and laboratory findings, resulting in the Erlangen Atopy Score (EAS). Objectives: To investigate the impacts of (i) atopic skin diathesis according to the EAS and (ii) the physician‐assessed diagnoses 'atopic dermatitis', 'allergic rhinitis' and 'allergic asthma' on SLS skin reactions. Methods: This is a retrospective analysis of data from 2030 consecutive patients patch tested with SLS (0·25% aqueous) from two tertiary referral centres in Germany, from 2008 to 2014. Results: Patients with a high probability of atopic skin diathesis showed no significant increase in positive SLS reactions compared with patients without atopic skin diathesis (14·2% vs. 16·8%). The grading of positive SLS skin reactions (1–4) revealed no differences in patients with or without atopic skin diathesis. Furthermore, diagnoses of atopic dermatitis, allergic rhinitis or allergic asthma had no impact on positive SLS skin reactions in multivariate logistic regression analysis. Conclusions: We found no association of increased skin irritability to SLS with atopic skin diathesis, atopic dermatitis, allergic rhinitis or allergic asthma in a large patient cohort. It therefore seems that the test of skin irritability with SLS, which is currently common practice in many centres, does not allow prediction of susceptibility to irritant eczematous inflammation in atopic vs. nonatopic individuals. What's already known about this topic? Irritant contact dermatitis and atopic skin diathesis share impaired skin barrier function as a pathophysiological pattern.Sodium lauryl sulfate (SLS) is tested at 0·25% aqueous as an irritant control in patch testing, and hence the results might be affected by atopic skin diathesis. What does this study add? Challenging a long‐standing paradigm, we found no association of increased reactivity to SLS patch tests in individuals with atopic skin diathesis, atopic dermatitis, allergic rhinitis or allergic asthma in a large patient cohort.Thus, irritant control testing with SLS, which is useful in interpreting doubtful allergen patch test results, does not depend on individual atopy status. Linked Comment: Agner and Elsner. Br J Dermatol 2020; 183:13. Plain language summary available online Respond to this article [ABSTRACT FROM AUTHOR]

Summary: Background: Earlier studies suggested an inverse association between contact allergy and psoriasis, although the results of clinical studies have been inconsistent. Gene expression studies in human contact allergy focusing on immune responses revealed nickel being an inducer of T helper (Th)1/Th17 and some Th22 immune polarization, whereas fragrances were found to promote a Th2‐dominated immune activation. Objectives: To investigate the epidemiological association between contact allergy and psoriasis in a large multicentre cohort and to analyse the sensitization profile to specific allergens in these patients. Methods: Retrospective analysis of patch‐tested patients from 56 departments of dermatology (1996–2015), including 2387 patients with psoriasis and 161 989 control patients. All patients with atopic dermatitis were excluded from both groups. Results: The odds ratio (OR) for contact allergy was calculated to be 0·55 in patients with psoriasis (95% confidence interval 0·50–0·59). Logistic regression analyses with several independent variables indicated a 'protective effect' of having psoriasis for most allergens, independently of age, sex, affected body site and patch test indication. Fragrance mix II (OR 0·36) and lanolin alcohols (OR 0·38) were found to be among the least common allergens in patients with psoriasis. In contrast, the frequency of contact dermatitis to nickel was only marginally affected in patients with psoriasis compared with controls (OR 0·75). Conclusions: The inverse association between psoriasis and allergic contact sensitization is likely to be not exclusively mediated by psoriasis itself. The polarization of the activated immune response by specific allergens may influence the occurrence and significance of contact allergies in underlying immune‐mediated diseases, eventually even beyond the skin. What's already known about this topic? Earlier studies suggested an inverse association between contact allergy and psoriasis, although the results have been inconsistent. What does this study add? Our findings revealed a significantly lower overall risk for contact sensitization in individuals with psoriasis.These results lend further support to the potential role of allergen‐specific immune polarization in contact dermatitis. Linked Comment:  Erfurt–Berge. Br J Dermatol 2019; 180:256–257. Plain language summary available online Respond to this article [ABSTRACT FROM AUTHOR]

Background As previous observations have indicated an inter-relationship between irritant and allergic skin reactions we analysed data of synchronous allergen and sodium lauryl sulfate ( SLS) patch tests in terms of a relationship between SLS responsiveness and allergic patch test reactions. Objectives To analyse differences in terms of allergen-specific and overall reaction profiles between patients with vs. those without an irritant reaction to SLS. Methods Clinical data of 26 879 patients patch tested from 2008 to 2011 by members of the Information Network of Departments of Dermatology were analysed. After descriptive analyses, including the MOAHLFA index, the positivity ratio and the reaction index, a negative binomial hurdle model was adopted to investigate the correlation between SLS reactivity and positive patch test reactions. Results Men, patients aged ≥ 40 years and patients with an occupational dermatitis background were over-represented in the SLS-reactive group. Patients with an irritant reaction to SLS showed a higher proportion of weak positive reactions, as well as more questionable and irritant reactions to contact allergens than patients not reactive to SLS. The risk of an additional positive patch test reaction increased by 22% for SLS-reactive patients compared with those who were SLS negative. Conclusions The marked association between SLS reactivity and the number of positive reactions in patch test patients may be due to nonspecific increased skin reactivity at the moment of patch testing only. However, increased SLS reactivity could also be due to longer-lasting enhanced skin irritability, which may have promoted (poly-)sensitization. Further studies, for example with longitudinal data on patients repeatedly patch tested with SLS and contact allergens, are necessary. [ABSTRACT FROM AUTHOR]

Linked Articles: Shuster. Br J Dermatol 2020; 183:1148. Heetfeld et al. Br J Dermatol 2020; 183:139–145 [ABSTRACT FROM AUTHOR]

Preservatives are well-known and important contact allergens. To examine the frequency of sensitization to preservatives, including time trends. Retrospective analysis of data on patch testing of preservatives contained in the standard series and special series collected by the IVDK during 1996-2009. Some 120 000 and 80 000 patients were tested with the baseline and the preservative series, respectively. Sensitization frequencies of the standard series allergens all ranged above 1%: methyldibromoglutaronitrile (MDBGN) 2·36-4·5%, methyl(chloro)isothiazolinone (MCI/MI) 2·22%, formaldehyde 1·54%, paraben mix 1·33% and Bronopol 1·25%. Regarding the special preservative series, 1·54% reacted positive to methylisothiazolinone (MI), and < 1% to the other preservatives. Concomitant reactions to formaldehyde in formaldehyde releasers ranged from 15% to almost 50%, and 67% of MI positives reacted to MCI/MI. As indicated by the MOAHLFA index, sensitization to MI, iodopropynylbutyl carbamate (IPBC) and quaternium 15 was associated more often with occupational dermatitis, whereas sensitization to imidazolidinyl urea and diazolidinyl urea was associated with face dermatitis, indicating cosmetic exposure. Epidemiologically relevant decreases (> 10%) were seen in chloroacetamide, benzyl alcohol and MDBGN. Epidemiologically relevant increases were noted in IPBC, sodium benzoate and MI. Preservatives are still important contact allergens. The introduction of new preservatives should consider the specific characteristics of occupational and of nonoccupational (cosmetic, household) exposure, and preventive measures should aim equally at both areas. [ABSTRACT FROM AUTHOR]

Background Late patch-test reactions, developing at day (D) 7 or later have been described for several allergens. Late reactions may reflect patch-test sensitization. Para-phenylenediamine (PPD) and epoxy resins (ER) are potent allergens and therefore may potentially induce patch-test sensitization. Up to now, there has been no prospective study on the frequency of late reactions in routine patch testing with these allergens. Objectives To assess the frequency of late reactions to PPD and ER. Patients/methods In 1748 patients PPD (PPD-base, 1% pet.) and ER [based on diglycidylether of bisphenol A (DGEBA, 1% pet.)], and in 812 patients, nickel sulphate (5% pet.) were removed from the test panel of the standard series and applied on the medial side of the upper arm. Patch-test occlusion time was 24 h in 588 (PPD and ER) and 241 patients (nickel sulphate), respectively, and 48 h in 1160 (PPD and ER) and 571 (nickel sulphate) patients, respectively. Patch tests were read on D1–3 and D2–3, respectively; additional late readings were performed on D7, D14 and D21 after patch-test application. Patients who were not able to return for all scheduled late readings were telephoned on D7, D14 or D21, and questioned about a reaction at the test sites. Patients were instructed to perform daily self-examination from D4 onwards and to return immediately to the clinic if a reaction at the upper arm became visible. Results Data of 1428 patients (ER and PPD) and 638 patients (nickel) were evaluable. In 25 patients (1·8%), patch tests became positive not before D7, among them 21 reactions to PPD (1·5%) and four reactions to ER (0·3%). In five of seven patients, repeated patch tests with PPD disclosed patch-test sensitization as the cause of the late reaction. All late reactions, except for one, occurred in patients in whom patch tests were applied for 48 h. No late reactions were seen with nickel sulphate. Conclusions PPD (1% pet.) elicited late reactions in 1·5% of routine patch tests, the majority of them probably being caused by patch-test sensitization. Therefore, the German Contact Dermatitis Research Group decided to remove PPD 1% pet. from the German standard series and to take efforts to optimize the patch-test conditions of PPD. One way to optimize PPD testing could be to reduce the exposure of PPD 1% to 24 h. Alternatively the patch-test concentration of PPD might be reduced. [ABSTRACT FROM AUTHOR]

There is evidence that a higher skin susceptibility may induce nonspecific erythematous or weak positive reactions to contact allergens in patch testing.To evaluate whether simultaneous application of sodium lauryl sulphate (SLS) along with diagnostic patch tests with contact allergens can provide information regarding skin irritability which may help to discriminate allergic from nonspecific irritant reactions to contact allergens.Between July 2001 and June 2003, this prospective study collected patch test data of 5971 patients from 19 centres in Germany and Austria in the Information Network of Departments of Dermatology (IVDK). In addition to contact allergens (standard series and eight known‘problematic’ allergens with a low reaction index and a high positivity ratio: 1,3-diphenylguanidine, amerchol L-101, benzalkonium chloride, benzoyl peroxide, cocamidopropyl betaine, octyl gallate, phenyl mercuric acetate and propylene glycol), patches with SLS 0·5% and 0·25% aq. were applied. Reactions to the allergens and to SLS were analysed at the IVDK data centre. The association between an erythematous or positive reaction to a certain allergen and an irritant reaction to SLS was assessed with logistic regression analysis, at the same time controlling for the influence of age and sex.Of the 29 allergens of the standard series, 23 and 21 gave a higher percentage of nonspecific erythematous reactions in patients with an irritant reaction to 0·25% and 0·5% SLS, respectively, in comparison with SLS-negative patients. All eight‘problematic’ allergens gave an increased percentage of nonspecific erythematous reactions. Similarly, 22 and 21 allergens of the standard series gave a higher percentage of positive allergic reactions in patients with an irritant reaction to 0·25% and 0·5% SLS, respectively, and seven of the eight‘problematic’ allergens gave a higher percentage of positive allergic rections (exception: octyl gallate). For most allergens, the markers of skin reaction (reaction index and positivity ratio) were worse in SLS-positive patients. Differences were more pronounced when testing with SLS 0·25% than with SLS 0·5%.Because there is a convincing association between skin irritability (evaluated by SLS test) and the degree of skin reaction to contact allergens, the SLS test may help in deciding whether a doubtful erythematous or weakly‘positive’ skin reaction should be interpreted as allergic or irritant. [ABSTRACT FROM AUTHOR]

Iodopropynyl butylcarbamate (IPBC) is a new preservative in medical and cosmetic leave-on products. Although cases of allergic contact dermatitis to IPBC have been reported, it is not known whether the usual test concentration of 0·1% is appropriate for screening tests with IPBC.To determine the concentration of IPBC that should be used in screening patch tests.An analysis was made of data filed by 26 centres of dermatology on patch tests performed with one or two concentrations of IPBC (0·1%, 0·2%, 0·3% or 0·5%) in 8106 unselected patients. Criteria used to determine the best test concentration of IPBC were the reaction index, the positivity ratio, the rate of crescendo reactions, and the relations between IPBC reactions and the MOAHLFA index irritant reactions to sodium lauryl sulphate (SLS), and allergic reactions to other contact allergens including preservatives.IPBC 0·1%, 0·2%, 0·3% and 0·5% yielded 0·5%, 0·8%, 1·3% and 1·7% positive reactions, but this increase was accompanied by an even greater increase in doubtful and irritant reactions. These figures and the other criteria examined suggested the range of suitable test concentrations of IPBC to lie between 0·2% and 0·3%. A detailed analysis of MOAHLFA indices and of associations between reactions to IPBC and reactions to other allergens and to SLS showed that most of the positive reactions to IPBC 0·2% can be assumed to be allergic ones and that with IPBC 0·2% fewer false-positive reactions can be expected than with IPBC 0·3%.Patch testing with IPBC 0·2% is suggested for patients with eczema possibly related to preservatives. [ABSTRACT FROM AUTHOR]

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Linked Article: Claßen et al. Br J Dermatol 2019; 180:315–320 [ABSTRACT FROM AUTHOR]