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Only few studies on contact allergy in African countries have been published. The aim of the present study was to provide an overview of the most common contact allergens identified by the use of patch tests in African countries based on a review of the existing literature. A total of twenty-four publications from eight African countries were initially identified by search in PubMed. The abstracts and method sections were screened, and 15 studies in which patch tests were actually used to identify the allergen causing the allergic contact dermatitis (ACD) were finally selected. Nickel, cobalt, chromium, fragrance mix and p-tert-butylphenol-formaldehyde resin were the dominating contact allergens responsible for 40%-90% of the positive patch test reactions. This study indicates that a targeted effort directed towards prevention, avoidance and regulation of reliably identified contact allergens could reduce the disease burden of ACD considerable in some African countries., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: CD8 + epidermal-resident memory T (T RM ) cells play central roles in local flare-up responses to experimental contact allergens by inducing massive influx of neutrophils to the epidermis upon allergen challenge. Whether similar immunopathogenic mechanisms are involved in the responses to clinically relevant contact allergens is unknown., Methods: The immune response to cinnamal, ρ-phenylenediamine (PPD) and methylisothiazolinone (MI) was studied in a well-established mouse model for allergic contact dermatitis that includes formation of T RM cells by ELISA, flow cytometry, fluorescence microscopy analyses and cell depletion protocols., Results: We show that the formation of CD4 + and CD8 + epidermal T RM cells and the inflammatory response are highly allergen-dependent. However, the magnitude of the flare-up responses correlated with the number of epidermal CD8 + T RM cells, CXCL1/CXCL2 release and recruitment of neutrophils to the epidermis. Finally, depletion of CD4 + T cells strongly enhanced the number of epidermal CD8 + T RM cells, the flare-up response and the epidermal infiltration of neutrophils for all allergens., Conclusion: As the first, this study demonstrates that clinically relevant contact allergens have the ability to generate pathogenic, epidermal CD8 + T RM cells that recruit neutrophils following re-exposure to the allergen, but that this normally is counteracted by the simultaneous induction of anti-inflammatory CD4 + T cells., (© 2023 The Authors. Contact Dermatitis published by John Wiley & Sons Ltd.)

Allergic contact dermatitis is one of the most frequent forms of skin inflammation. Very often, we are exposed to mixtures of allergens with varying potencies, doses/areas, and exposure times. Therefore, improved knowledge about immune responses to combinations of contact allergens is highly relevant. In this article, we provide a general introduction to immune responses to contact allergens, and discuss the literature concerning immune responses to mixtures of allergens. According to the existing evidence, increased responses are induced following sensitization with combinations of allergens as compared with single allergens. The response to a mixture of allergens can be both additive and synergistic, depending on the dose and combination of allergens. Importantly, sensitization with combinations of either fragrance allergens or metal salts can result in increased challenge responses to specific allergens within the mixture. Taken together, the immune responses to mixtures of allergens are complex, and further studies are required to obtain the necessary knowledge to improve consumer safety., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Contact allergy is characterized by local skin inflammation that, in some cases, can result in systemic immune activation., Objectives: To investigate whether IVIS SpectrumCT analyses can be used to detect the immune response induced by contact allergens., Methods: Mice were repeatedly exposed to vehicle or allergens on the ears. The local and systemic responses were analysed at different times with the ProSense 750 FAST probe in IVIS SpectrumCT measurements. In addition, changes in ear thickness, cytokine profile in the skin and immunological phenotype in the draining lymph nodes and spleen were determined., Results: Local inflammation was detected by ProSense 750 FAST and correlated with changes in ear thickness, cytokine profile and immunological phenotype following exposure to the strong contact allergen 2,4-dinitrofluorobenzene. Analysis of the systemic response with ProSense 750 FAST did not show any difference between allergen-exposed and control mice, although fluorescence-activated cell sorting analysis of the spleen showed increased numbers of γδ T cells and CD11b + CD11c + MHCII + cells in allergen-treated mice., Conclusions: IVIS SpectrumCT analyses with ProSense 750 FAST as the probe can be used to detect local immune responses induced by contact allergens., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Perfumes are complex mixtures composed of many fragrance ingredients, many of which are known to be only weak allergens when tested individually. It is therefore surprising that fragrance contact allergy is one of the most common forms of contact allergy., Objectives: To investigate whether mixing different fragrance allergens leads to increased sensitization potency, and to examine the difference in the challenge response to one chemical in mice sensitized either with the mixture of allergens or with only the relevant allergen., Methods: CBA mice were sensitized with three different concentrations of three fragrance allergens alone or as a mixture. The sensitization and elicitation responses were measured by ear thickness plus infiltration of B and T cells and T cell proliferation in the draining lymph nodes., Results: We found a dose-dependent sensitization response for each of the allergens. An increased response was seen when the allergens were mixed. A stronger challenge response to cinnamal was seen in mice sensitized with the allergen mixture than in mice sensitized with cinnamal alone., Conclusions: Our findings suggest that mixtures of allergens increase the primary response that potentiates the generation of memory T cells in response to the specific allergen. Thus, allergen mixtures enhance both induction and elicitation of contact allergy., (© 2011 John Wiley & Sons A/S.)

Background: CD8+ epidermal‐resident memory T (TRM) cells play central roles in local flare‐up responses to experimental contact allergens by inducing massive influx of neutrophils to the epidermis upon allergen challenge. Whether similar immunopathogenic mechanisms are involved in the responses to clinically relevant contact allergens is unknown. Methods: The immune response to cinnamal, ρ‐phenylenediamine (PPD) and methylisothiazolinone (MI) was studied in a well‐established mouse model for allergic contact dermatitis that includes formation of TRM cells by ELISA, flow cytometry, fluorescence microscopy analyses and cell depletion protocols. Results: We show that the formation of CD4+ and CD8+ epidermal TRM cells and the inflammatory response are highly allergen‐dependent. However, the magnitude of the flare‐up responses correlated with the number of epidermal CD8+ TRM cells, CXCL1/CXCL2 release and recruitment of neutrophils to the epidermis. Finally, depletion of CD4+ T cells strongly enhanced the number of epidermal CD8+ TRM cells, the flare‐up response and the epidermal infiltration of neutrophils for all allergens. Conclusion: As the first, this study demonstrates that clinically relevant contact allergens have the ability to generate pathogenic, epidermal CD8+ TRM cells that recruit neutrophils following re‐exposure to the allergen, but that this normally is counteracted by the simultaneous induction of anti‐inflammatory CD4+ T cells. [ABSTRACT FROM AUTHOR]

Background: Allergic contact dermatitis (ACD) is classically described as a delayed‐type hypersensitivity reaction. However, patients often experience flare‐ups characterized by itching erythema, edema, and often vesicles occurring within hours after re‐exposure of previously sensitized skin to the specific contact allergen. Recent studies have indicated that skin‐resident memory T (TRM) cells play a central role in ACD. However, the pathogenic role of TRM cells in allergen‐induced flare‐ups is not known. Methods: By the use of various mouse models and cell depletion protocols, we investigated the role of epidermal TRM cells in flare‐up reactions to the experimental contact allergen 1‐fluoro‐2,4‐dinitrobenzene. The inflammatory response was measured by changes in ear thickness, and the cellular composition in epidermis was determined by flow cytometry and confocal microscopy. Finally, adaptive transfer and inhibitors were used to determine the role of TRM cells, neutrophils, and CXCL1/CXCL2 in the response. Results: We show that CD8+ TRM cells initiate massive infiltration of neutrophils in the epidermis within 12 h after re‐exposure to the contact allergen. Depletion of neutrophils before re‐exposure to the allergen abrogated the flare‐up reactions. Furthermore, we demonstrate that CD8+ TRM cells mediate neutrophil recruitment by inducing CXCL1 and CXCL2 production in the skin, and that blockage of the C‐X‐C chemokine receptor type 1 and 2 inhibits flare‐up reactions and neutrophil infiltration. Conclusion: As the first, we show that epidermal CD8+ TRM cells cause ACD flare‐ups by rapid recruitment of neutrophils to the epidermis. [ABSTRACT FROM AUTHOR]

Interleukin‐1β (IL‐1β) is an important pro‐inflammatory cytokine that has an effect on almost every cell lineage in the body. By blocking IL‐1β and investigating the IL‐1β signaling pathway, several studies have demonstrated a central role of IL‐1β in the response to contact allergens. This review summarizes the current literature regarding the basic immunological mechanisms mediated by IL‐1β in the different phases of allergic contact dermatitis (ACD) and highlights potential IL‐1β‐targeted treatment options, which in the future may be relevant in the treatment of patients with ACD. This review is based primarily on studies using various mouse models and human in vitro studies, since clinical studies on the effect of IL‐1β in ACD are lacking. [ABSTRACT FROM AUTHOR]

Background Contact allergy is characterized by local skin inflammation that, in some cases, can result in systemic immune activation. Objectives To investigate whether IVIS SpectrumCT analyses can be used to detect the immune response induced by contact allergens. Methods Mice were repeatedly exposed to vehicle or allergens on the ears. The local and systemic responses were analysed at different times with the ProSense 750 FAST probe in IVIS SpectrumCT measurements. In addition, changes in ear thickness, cytokine profile in the skin and immunological phenotype in the draining lymph nodes and spleen were determined. Results Local inflammation was detected by ProSense 750 FAST and correlated with changes in ear thickness, cytokine profile and immunological phenotype following exposure to the strong contact allergen 2,4-dinitrofluorobenzene. Analysis of the systemic response with ProSense 750 FAST did not show any difference between allergen-exposed and control mice, although fluorescence-activated cell sorting analysis of the spleen showed increased numbers of γδ T cells and CD11b+ CD11c+ MHCII+ cells in allergen-treated mice. Conclusions IVIS SpectrumCT analyses with ProSense 750 FAST as the probe can be used to detect local immune responses induced by contact allergens. [ABSTRACT FROM AUTHOR]

Background Atranol and chloroatranol are the main allergens of oakmoss absolute. However, the immune responses induced by these substances are poorly characterized. Objectives To characterize immune responses induced by atranol, chloroatranol and oakmoss absolute in mice. Methods Mice were sensitized and challenged with various concentrations of atranol, chloroatranol, and oakmoss absolute. The immune responses were analysed as B cell infiltration, T cell proliferation in the draining lymph nodes, and expression of interleukin ( IL)-18, IL-1β and tumour necrosis factor-α in skin. The cytotoxicity of atranol and chloroatranol against keratinocytes was determined. Results Sensitization experiments showed that atranol, chloroatranol and oakmoss induced sensitization when applied in high concentrations. Challenge experiments showed that even low concentrations of atranol and chloroatranol induced sensitization. In parallel, atranol and chloroatranol elicited challenge reactions following sensitization with oakmoss. The magnitude of the immune response to the three allergens increased in the following order: atranol, chloroatranol, and oakmoss. The expression of proinflammatory cytokines was induced by chloroatranol and oakmoss, but not by atranol. Chloroatranol was found to be more cytotoxic than atranol against keratinocytes. Conclusions Atranol and chloroatranol can elicit both sensitization and challenge reactions, but the mixture of allergens in oakmoss absolute is more potent than atranol and chloroatranol alone. [ABSTRACT FROM AUTHOR]