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Background: Metal alloys containing contact sensitizers (nickel, palladium, titanium) are extensively used in medical devices, in particular dentistry and orthopaedic surgery. The skin patch test is used to test for metal allergy. Objective: To determine whether metal salts, when applied to freshly excised skin at patch test–relevant concentrations and using a method which mimics skin patch testing, cause in changes in the epidermis and dermis. Methods: Tissue histology, apoptosis, metabolic activity, and inflammatory cytokine release were determined for two nickel salts, two palladium salts, and four titanium salts. Results: Patch test–relevant concentrations of all metal salts caused localized cytotoxicity. This was observed as epidermis separation at the basement membrane zone, formation of vacuoles, apoptotic nuclei, decreased metabolic activity, and (pro)inflammatory cytokine release. Nickel(II) sulfate hexahydrate, nickel(II) chloride hexahydrate, titanium(IV) bis(ammonium lactato)dihydroxide, and calcium titanate were highly cytotoxic. Palladium(II) chloride, sodium tetrachloropalladate(II), titanium(IV) isopropoxide, and titanium(IV) dioxide showed mild cytotoxicity. Conclusion: The patch test in itself may be damaging to the skin of the patient being tested. These results need further verification with biopsies obtained during clinical patch testing. The future challenge is to remain above the elicitation threshold at noncytotoxic metal concentrations. [ABSTRACT FROM AUTHOR]

Background: The number of people within the European population having at least one tattoo has increased notably, and with it the number of tattoo‐associated clinical complications. Despite this, safety information and testing regarding tattoo inks remain limited. Objective: To assess cytotoxicity and sensitization potential of 16 tattoo inks after intradermal injection into reconstructed human skin (RHS). Methods: Commercially available tattoo inks were injected intradermally into RHS (reconstructed epidermis on a fibroblast‐populated collagen hydrogel) using a permanent makeup device. RHS biopsies, tissue sections, and culture medium were assessed for cytotoxicity (thiazolyl blue tetrazolium bromide assay [MTT assay]), detrimental histological changes (haematoxylin and eosin staining), and the presence of inflammatory and sensitization cytokines (interleukin [IL]‐1α, IL‐8, IL‐18; enzyme‐linked immunosorbent assay). Results: Varying degrees of reduced metabolic activity and histopathological cytotoxic effects were observed in RHS after ink injection. Five inks showed significantly reduced metabolic activity and enhanced sensitization potential compared with negative controls. Discussion: Using the RHS model system, four tattoo inks were identified as highly cytotoxic and classified as potential sensitizers, suggesting that allergic contact dermatitis could emerge in individuals carrying these inks. These results indicate that an RHS‐based assessment of cytotoxicity and sensitization potential by intradermal tattoo ink injection is a useful analytical tool to determine ink‐induced deleterious effects. [ABSTRACT FROM AUTHOR]

Background: The nature of clinically related adverse reactions to titanium is still unknown. Objective: To determine whether titanium salts have irritant or sensitizing potential in a reconstructed human skin (RHS) model with integrated Langerhans cells (LCs). Methods: RHS‐LCs (ie, reconstructed epidermis) containing primary differentiated keratinocytes and CFSE+CD1a+‐LCs generated from the MUTZ‐3 cell line on a primary fibroblast‐populated collagen hydrogel (dermis) were topically exposed to titanium(IV) bis(ammonium lactato)dihydroxide (TiALH). LC migration and plasticity were determined. Results: TiALH resulted in CFSE+CD1a+‐LC migration out of the epidermis. Neutralizing antibodies to CCL5 and CXCL12 showed that LC migration was CCL5 and not CXCL12 mediated. LCs accumulating within the dermis after TiALH exposure were CFSE+Lang+CD68+ which is characteristic of a phenotypic switch of MUTZ‐LC to a macrophage‐like cell. Furthermore, TiALH did not result in increased interleukin (IL)‐1β or CCR7 messenger RNA (mRNA) in the dermis, but did result in increased IL‐10 mRNA. In addition, monocultures of MUTZ‐LCs failed to increase LC maturation biomarkers CD83, CD86, and CXCL‐8 when exposed to noncytotoxic concentrations of four different titanium salts. Conclusion: These results classify titanium salts as irritants rather than sensitizers and indicate that titanium implant‐related complaints could be due to localized irritant‐mediated inflammation arising from leachable agents rather than a titanium metal allergy. [ABSTRACT FROM AUTHOR]

A modified local lymph node assay (LLNA) with ex vivo tritium thymidine (3H-TdR) labeling of the proliferating lymph node cells was used for determination of the allergenic potency of chemicals used in the production of rubber for latex medical gloves. Fifteen chemicals known to induce contact hypersensitivity reactions in man, including various thiuram, carbamate, and benzothiazole compounds, and one amine were tested. The EC3 (effective concentration inducing a 3-fold increase in proliferation of lymph node cells [Stimulation Index, SI = 3]) was calculated with nonlinear regression analysis, including a bootstrap method for determination of the 5–95% confidence interval of the EC3 value. This procedure identified 14 out of the 15 chemicals tested as sensitizers, while for one chemical, ZDBC, no EC3 could be calculated due to low responses and a lack of a dose-response relationship in the data obtained. The ranking order of the chemicals with increasing EC3 values (and thus decreasing allergenic potency) was found to be in the following order: ZDEC < TMTD < TETD < ZPC < ZDMC < MBTS < PTD < TMTM < MBT < MBI < PTT < ZMBT < TBTD < DEA < ZDBC. Our results indicate that the chemicals of choice for use in the production of natural rubber latex products would be for the thiuram compounds, TBTD; for the carbamates, ZDBC; and for the benzothiazoles, ZMBT. However, one has to be aware that besides potency, the total amount of residual chemical present in the final product is also important for allergy induction. [ABSTRACT FROM PUBLISHER]

Allergic and irritant skin reactions caused by topical exposure to permanent hair dyes are a common problem. For regulatory and ethnical purposes, it is required to perform chemical safety assessment following the replacement, reduction, and refinement of animal testing (3Rs). Permanent hair dyes are formed by a mixture of ingredients that vary from low to extreme skin sensitizing potency and that inter-react to form unknown by-products. Because of the complex reaction, this cytotoxic mechanism has not yet been elucidated and is the subject of this study. Here, we topically exposed p -phenylenediamine (PPD), Resorcinol (RES), Hydrogen Peroxide (H 2 O 2 ) alone or as a mixture to RhE and evaluated parameters related to skin irritation such as epidermal viability, keratinocytes damage, barrier loss and IL-1 α. Our data indicates that ingredients tested alone did not lead to an increase of cytotoxic parameters related to skin irritation. However, when the mixture of PPD/H 2 O 2 /RES and PPD/H 2 O 2 was applied to the RhE, some of the parameters such as morphological changes including the presence of apoptotic cells, barrier loss and increased IL- 1 α release were observed. The results indicate that the mixture of ingredients used in permanent hair dyes have an irritant effect in RhE while the ingredients alone not. [ABSTRACT FROM AUTHOR]