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Background: Studies on patch testing with workplace materials and evaluation of current occupational relevance of positive patch test reactions are scarce in patients with occupational dermatitis (OD). Objectives: To identify frequent sensitizations with occupational relevance and to determine the value of patch testing with workplace materials in OD patients. Patients and Methods: Results and clinical data of 654 patients with suspected OD patch tested between 2013 and 2017 were analysed. Results: Occupational allergic contact dermatitis was diagnosed in 113 (17.3%) patients. Mechanics had the widest range of occupational sensitizations. Sensitization to epoxy resin was rated occupationally relevant in almost all handicraft trades. Among positive patch test reactions to workplace products, those to water‐based metal working fluids and leave‐on cosmetic products were most frequent. Despite frequent testing, protective gloves only rarely elicited positive reactions. Preservatives and rubber compounds were most frequently identified as currently occupationally relevant. Conclusions: Rubber allergy is occupationally relevant especially in healthcare workers and cleaners. Generally, preservatives including formaldehyde releasers are important allergens in OD patients. Leave‐on cosmetic products must not be forgotten as allergen sources. Patch testing both workplace materials and standardized test preparations has a complementary value and is beneficial for the diagnostic work‐up of OD patients. Highlights: Patch testing of workplace materials and standardized test preparations has a complementary value in the diagnostic work‐up of occupational dermatitis patients.Mechanics should be patch tested in a broad fashion, including rubber, metal working fluids, epoxy resin systems, and leave‐on products.Epoxy resin systems exhibit current occupational relevance in almost all high‐risk professions of the handicraft sector. [ABSTRACT FROM AUTHOR]

Background: Filaggrin (Flg) and hornerin (Hrnr) share similar structural and functional features. Both proteins have been implicated as essential proteins for skin barrier maintenance. Loss‐of‐function mutations of these genes constitute a risk factor for atopic dermatitis and eczema‐related asthma. Furthermore, both FLG and HRNR protein levels are downregulated in patients with atopic dermatitis. Thus, mice deficient for Flg and Hrnr provide a novel model to study skin barrier impairment and the susceptibility for cutaneous inflammation. Methods: By using appropriate targeting vectors and breeding strategies, we established a homozygous FlgHrnr double‐deficient (FlgHrnr−/−) mouse model lacking both genes including the intergenomic sequence. Results: Neonates appeared normal, but developed a transient scaly phenotype with overall flaky appearance, but no overt skin phenotype in adulthood, thereby reflecting a subclinical barrier defect seen in humans. Structurally, FlgHrnr−/− mice displayed a markedly reduced granular layer and a condensed cornified layer. Functionally, FlgHrnr−/− mice showed permeability abnormalities and metabolic aberrations regarding the production of natural moisturizing factors (NMFs) in the stratum corneum. Surprisingly, although the immune system revealed no aberrations under steady‐state conditions, FlgHrnr−/− mice are predisposed to mount an allergic contact dermatitis, especially at hapten threshold levels eliciting allergic reactions. Conclusions: Together, our FlgHrnr−/− mouse model nicely reflects the epicutaneous sensitization susceptibilities and inflammatory reactions to environmental insults in humans with impaired skin barrier functions. [ABSTRACT FROM AUTHOR]

Psoriasis is characterized by an apoptosis-resistant and metabolic active epidermis, while a hallmark for allergic contact dermatitis (ACD) is T cell-induced keratinocyte apoptosis. Here, we induced ACD reactions in psoriasis patients sensitized to nickel (n = 14) to investigate underlying mechanisms of psoriasis and ACD simultaneously. All patients developed a clinically and histologically typical dermatitis upon nickel challenge even in close proximity to pre-existing psoriasis plaques. However, the ACD reaction was delayed as compared to non-psoriatic patients, with a maximum intensity after 7 days. Whole genome expression analysis revealed alterations in numerous pathways related to metabolism and proliferation in non-involved skin of psoriasis patients as compared to non-psoriatic individuals, indicating that even in clinically non-involved skin of psoriasis patients molecular events opposing contact dermatitis may occur. Immunohistochemical comparison of ACD reactions as well as in vitro secretion analysis of lesional T cells showed a higher Th17 and neutrophilic migration as well as epidermal proliferation in psoriasis, while ACD reactions were dominated by cytotoxic CD8+ T cells and a Th2 signature. Based on these findings, we hypothesized an ACD reaction directly on top of a pre-existing psoriasis plaque might influence the clinical course of psoriasis. We observed a strong clinical inflammation with a mixed psoriasis and eczema phenotype in histology. Surprisingly, the initial psoriasis plaque was unaltered after self-limitation of the ACD reaction. We conclude that sensitized psoriasis patients develop a typical, but delayed ACD reaction which might be relevant for patch test evaluation in clinical practice. Psoriasis and ACD are driven by distinct and independent immune mechanisms. [ABSTRACT FROM AUTHOR]

Background: A type-IV-allergic reaction to German camomile (Matricaria chamomilla) in a form of allergic contact dermatitis is not unusual. However, only a few cases of anaphylactic reaction to camomile have been described in the literature. Case Summary: We present the case of a 38-year-old Caucasian man who developed an episode of severe anaphylaxis with generalized urticaria, angioedema and severe dyspnoea one hour after consuming camomile tea. Laboratory examination demonstrated a total serum IgE of 123 kU/I with specific IgE against camomile (4.94 kU/I, class 3). Skin prick test and labial provocation test with camomile showed a strong positive reaction. Discussion: Our case confirms the presence of a type-I allergy to orally ingested camomile and indicates that the incidence and risk may be underestimated. Additional response to mugwort and pollen-derived food allergens should be evaluated in patients sensitised to camomile due to a higher incidence of allergic cross-reactivity. [ABSTRACT FROM AUTHOR]