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The skin is our interface with the outside world and consequently it is exposed to a wide range of microbes and allergens. Recent studies have indicated that allergen-specific skin-resident memory T (TRM) cells play a role in allergic contact dermatitis (ACD). However, the composition and dynamics of the epidermal T cell subsets during ACD are not known. Here we show that exposure of the skin to the experimental contact allergen 1-fluoro-2,4-dinitrobenzene (DNFB) results in a displacement of the normally occurring dendritic epidermal T cells (DETC) concomitant with an accumulation of epidermal CD8+CD69+CD103+ TRM cells in mice. By studying knock-out mice, we provide evidence that CD8+ T cells are required for the displacement of the DETC and furthermore, that DETC are not required for recruitment of CD8+ TRM cells to the epidermis following allergen exposure. We demonstrate that the magnitude of the allergic reaction correlates with the number of CD8+ epidermal TRM cells that again correlates with allergen dose and number of allergen exposures. Finally, in an attempt to elucidate why CD8+ epidermal TRM cells persist in the epidermis, we show that CD8+ epidermal TRM cells have a higher proliferative capability and are bioenergetically more stable, displaying a higher spare respiratory capacity than DETC.

Background: Exposure to metalworking fluids (MWFs) is a well-known cause of occupational contact dermatitis. Objectives: We aimed to (1) determine the amount of nickel, chromium, and cobalt in large samples of used and unused MWFs collected from metalworking plants in Denmark, and (2) evaluate a handheld x-ray fluorescence (XRF) device as a screening instrument for metals in MWFs. Methods: A handheld XRF device was used to screen for metals in MWFs. All samples were also analyzed for concentrations of nickel, chromium, and cobalt using graphite furnace atomic absorption spectroscopy (GFAAS). Results: GFAAS analysis showed that 13 of 80 samples (16.3%) contained >1 mg/kg (ppm) nickel (range: 6.4-17.7 mg/kg), 3 of 80 (3.8%) contained >1 (range: 1.4-3.1) mg/kg chromium, and 1 of 80 (1.3%) contained 1.3 mg/kg cobalt. XRF-screening detected nickel in eight samples (range: 2.5-15.5 mg/kg), but only one sample with 3.0 (±0.5) mg/kg was found subsequently to contain 9.9 (0.02) mg/kg nickel by GFAAS. Although no chromium was found by XRF analysis, cobalt was found in two samples with 6 (±1.5) mg/kg and 5 (±1.5) mg/kg, subsequently found to contain 0.1 (±0.01) mg/kg and 0.08 (±0.01) mg/kg by GFAAS. Similar concentrations of nickel were found in used (N = 6, range: 6.4-17.7 mg/kg) and unused MWFs (N = 7, range: 9.1-17.3 mg/kg). Conclusion: Considerable levels of nickel, chromium, and cobalt were found in some used and unused MWFs indicating that these might represent a source of metal allergy. The XRF device is a poor screening test for these metals in MWFs.

Occupational hand eczema is common among hairdressers, and protective gloves are important in limiting exposure to irritants and allergens. Various glove types may differ in their protective ability, and their use may lead to hand eczema due to skin irritancy and allergy. MEDLINE was searched for studies investigating permeation of gloves to irritants and allergens used in the hairdressing trade, as well as adverse effects of glove use affecting hairdressers. Forty-four studies were identified; nine reported on permeation. Of those, two in vitro studies found nitrile rubber (NR) gloves to give the best protection when handling hair dyes. Polyethylene (PE) gloves had the lowest reported break-through time. The prevalence of sensitization to rubber materials in European hairdressers was as follows: thiuram mix, median 2.5% (range 0%-8.2%), weighted average 3.0% (95% confidence interval [CI] 3.0%-3.1%); mercapto mix, median 0.4% (range 0%-3.3%), weighted average 0.5% (95% CI 0.47%-0.50%), mercaptobenzothiazole, median 0.6% (range 0%-6.6%), weighted average 0.7% (95% CI 0.6%-0.7%), NRL-type I allergy, median 1.3% (range 1%-16.4%), weighted average 4.0% (95% CI 3.6%-4.5%). In conclusion, NR gloves provide the best skin protection for hairdressers, although natural rubber latex (NRL) and polyvinylchloride (PVC) gloves may be sufficient in most cases. PE gloves are not recommended. Synthetic rubber gloves with low or no levels of accelerators are preferred.

Background: Aluminum contact allergy is mostly seen in children with vaccination granulomas, following immunization with aluminum-adsorbed childhood vaccines. Objectives: To characterize a cohort of children with vaccination granulomas and aluminum allergy concerning early life conditions, exacerbating factors, avoidance behavior, treatments, and potential impact on quality of life. Methods: A questionnaire study was conducted among 177 children aged 0 to 15 years with vaccination granulomas and aluminum allergy, and a reference group of 61 children aged 3 to 14 years with various types of dermatitis undergoing patch testing. Results: All children in the granuloma group were reportedly affected by itch. Infection exacerbated the itch in 59%. Other worsening factors were eating tin-foiled/canned food (31%) and use of aluminum-containing sunscreen (46%). Many parents took precautions to avoid aluminum exposure. Children with granulomas were more likely to be nonadherent to the National Vaccination Program than the reference group (27% vs 2%, P <.001). Parents in the granuloma group reported a decreased life quality for both parents and children compared with the reference group. Conclusions: Itching vaccination granulomas and aluminum allergy have a considerable negative impact on affected children and their families, causing avoidance behavior, reduced adherence to vaccination programs, and a negative effect on the overall life quality.

BACKGROUND: p-Phenylenediamine (PPD) is a strong contact allergen used in hair dye that is known to cause allergic contact dermatitis (ACD). Both private and occupational exposure to PPD is frequent, but the effect of PPD exposure in nonallergic occupationally exposed subjects is unknown.OBJECTIVE: We sought to investigate the effects of PPD exposure on the skin of occupationally exposed subjects with and without clinical symptoms.METHODS: Skin biopsy specimens were collected from 4 patients with mild and 5 patients with severe PPD-related ACD and 7 hairdressers without contact dermatitis on day 4 after patch testing with 1% PPD in petrolatum. RNA sequencing and transcriptomics analyses were performed and confirmed by using quantitative RT-PCR. Protein expression was analyzed in skin from 4 hairdressers and 1 patient with ACD by using immunofluorescence staining. Reconstructed human epidermis was used to test the effects of PPD in vitro.RESULTS: RNA sequencing demonstrated downregulation of tight junction and stratum corneum proteins in the skin of patients with severe ACD after PPD exposure. Claudin-1 (CLDN-1), CLDN8, CLDN11, CXADR-like membrane protein (CLMP), occludin (OCLN), membrane-associated guanylate kinase inverted 1 (MAGI1), and MAGI2 mRNA expression was downregulated in patients with severe ACD. CLDN1 and CLMP expression were downregulated in nonresponding hairdressers and patients with mild ACD. Filaggrin 1 (FLG1), FLG2, and loricrin (LOR) expression were downregulated in patients with ACD. Confocal microscopic images showed downregulation of CLDN-1, FLG-1, and FLG-2 expression. In contrast, 3-dimensional skin cultures showed upregulation of FLG-1 in response to PPD but downregulation of FLG-2.CONCLUSION: PPD-exposed skin is associated with extensive transcriptomic changes, including downregulation of tight junction and stratum corneum proteins, even in the absence of clinical symptoms.

BACKGROUND: There is currently no agreed cosmetic series for use across Europe.OBJECTIVES: To establish allergens currently tested in local and national cosmetic series.METHOD: Members of the European Surveillance System on Contact Allergy and the European Cooperation in Science and Technology project TD1206 ("StanDerm") were surveyed to establish their current practice.RESULTS: A wide range of allergens was tested but there was significant variation between centres on the allergens considered to be important in screening for allergy to cosmetics. The number of allergens tested in addition to the baseline series varied between 2 and 50.CONCLUSIONS: There is a need for further investigation to establish the frequency and relevance of reactions to cosmetic allergens to enable an agreed evidence-based cosmetic series to be produced. Criteria for inclusion need to be established.

Background: Naturally derived cosmetic product ingredients of both plant and animal origin are being included increasingly in product formulations in order to cater to consumer preferences. They may be an overlooked cause of reactions to cosmetic products in some patients with dermatitis. Objectives: To identify naturally derived cosmetic product ingredients with allergenic potential (type I and type IV) and propose a cosmetic screening test series. Methods: The study was conducted in two steps. The first step was a market survey using a nonprofit application helping consumers avoid problematic substances in cosmetic products. The application contained 10 067 cosmetic products that were label checked for naturally derived cosmetic product ingredients. The second step was a literature search to examine how frequently the naturally derived ingredients were described and related to allergic reactions in cosmetics or other topically administered products. Results: We identified 121 different naturally derived cosmetic product ingredients that were included in at least 30 cosmetic products. In total, 22 ingredients were selected for a screening test series. Conclusions: We propose a supplemental patch test and a prick test screening series with naturally derived cosmetic product ingredients for patients with skin reactions to cosmetic products, aiming to identify a cause in more patients than is currently possible.