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The role of the microbiome in the molecular mechanisms underlying allergy has become highly relevant in recent years. Studies areincreasingly suggesting that altered composition of the microbiota, or dysbiosis, may result in local and systemic alteration of the immuneresponse to specific allergens. In this regard, a link has been established between lung microbiota and respiratory allergy, between skinmicrobiota and atopic dermatitis, and between gut microbiota and food allergy.The composition of the human microbiota is dynamic and depends on host-associated factors such as diet, diseases, and lifestyle. Omics arethe techniques of choice for the analysis and understanding of the microbiota. Microbiota analysis techniques have advanced considerablyin recent decades, and the need for multiple approaches to explore and comprehend multifactorial diseases, including allergy, has increased.Thus, more and more studies are proposing mechanisms for intervention in the microbiota.In this review, we present the latest advances with respect to the human microbiota in the literature, focusing on the intestinal, cutaneous,and respiratory microbiota. We discuss the relationship between the microbiome and the immune system, with emphasis on allergic diseases.Finally, we discuss the main technologies for the study of the microbiome and interventions targeting the microbiota for prevention of allergy. (AU)

El papel del microbioma en los mecanismos moleculares de las enfermedades alérgicas se ha vuelto muy relevante en los últimos años.Cada vez más estudios sugieren que una composición alterada de la microbiota, o disbiosis, puede resultar en una alteración local ysistémica de la respuesta inmune a alérgenos específicos. En este sentido, se ha establecido un vínculo entre la microbiota pulmonar y laalergia respiratoria, así como la microbiota cutánea y el desarrollo de dermatitis atópica, y la microbiota intestinal y la alergia alimentaria.La composición de la microbiota humana es dinámica y depende de diversos factores asociados al huésped como la dieta, las enfermedadesy el estilo de vida, entre otros. Para el análisis y comprensión de la microbiota, las ómicas son las técnicas de elección. En las últimasdécadas, las técnicas de análisis de microbiota han tenido un gran avance y han aumentado la necesidad de múltiples enfoques paraexplorar y comprender las enfermedades multifactoriales, incluidas las enfermedades alérgicas. De esta manera, cada vez son más losestudios que proponen mecanismos de intervención sobre la microbiota de pacientes.En esta revisión, presentamos los últimos avances encontrados en la literatura sobre la microbiota humana, centrándose en las microbiotasintestinal, cutánea y respiratoria. Discutimos la relación entre el microbioma y el sistema inmunológico, con especial énfasis en lasenfermedades alérgicas. Finalmente, discutimos las principales tecnologías para el estudio del microbioma y los estudios de intervencióndirigidos a la microbiota propuestos para la prevención de alergias. (AU)

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INTRODUCTION: Hand eczema is a frequent disease in adults. Diagnosing the cause of hand eczema is difficult due to different classifications. There is lack of evidence on hand eczema and its causes in children. MATERIAL AND METHOD: A total of 389 children between 0 and 16 years were identified between 1996 and 2016, from whom 42 (10.8%) with exclusively hand eczema were selected. In all cases a standard battery of epicutaneous patch tests was performed, as well as additional batteries depending on the clinical suspicion. The clinical and epidemiological features of these children were recorded and compared against children with eczema in other locations. RESULTS: The 42 children with hand eczema included 25 (60.5%) girls, and 17 (40.5%) boys, with a mean age of 10.6 +- 3.9 years, and did not differ from that of children with eczema in other locations. The definitive diagnosis after patch-testing was Atopic Dermatitis in 15 cases, Allergic Contact Dermatitis in 14 patients, Endogenous Vesiculous Eczema in 6 cases, Endogenous Hyperkeratotic Eczema in 5 cases, and Irritant Contact Dermatitis in 2 cases. The most frequent allergens detected were thiomersal (9 cases), nickel (5 cases), mercury (5 cases), and cobalt (4 cases). CONCLUSION: Hand eczema is a common condition in children. The most common cause is atopic dermatitis, although cases of allergic contact dermatitis manifesting as hand eczema are not uncommon. Any child with eczema of hands in whom an allergic cause is suspected should be referred for patch- testing.

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BACKGROUND: Few epidemiological studies have investigated the incidence of allergic contact dermatitis in children. Underdiagnosis has been observed in some studies, with many cases in which the condition is not suspected clinically and patch tests are not performed. However, the prevalence of pediatric sensitization to allergens has been reported to be as high as 20%, and the diagnosis should therefore be contemplated as a possibility in this age group. MATERIAL AND METHODS: We performed a retrospective analysis of the skin allergy database of the Dermatology Department of Consorcio Hospital General Universitario de Valencia. Children between 0 and 16 years of age diagnosed with allergic contact dermatitis in the previous 15 years (between 2000 and 2015) were included in the analysis. Epidemiological (age, sex, history of atopy) and clinical (site of the lesions, allergen series applied, positive reactions, and their relevance) variables were gathered. RESULTS: Patch tests had been performed on 4,593 patients during the study period. Of these, 265 (6%) were children aged between 0 and 16 years. A positive reaction to at least one of the allergens tested was observed in 144 (54.3%) patients in that group. The allergens most frequently identified were the following (in decreasing order of frequency): thiomersal, cobalt chloride, colophony, paraphenylenediamine, potassium dichromate, mercury, and nickel. The sensitization was considered relevant in 177 (61.3%) cases. CONCLUSIONS: More than half of the children studied showed sensitization to 1 or more allergens, with a high percentage of relevant sensitizations. All children with a clinical suspicion of allergic contact dermatitis should be referred for patch testing. As no standardized test series have been developed for this age group, a high level of clinical suspicion and knowledge of the allergens most commonly involved are required when selecting the allergens to be tested.

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INTRODUCTION: Henna tattoos are a very common practice in the adolescent population. Henna is very often admixed with para-phenylenediamine (PPDA) to improve the appearance of the tattoo. PPDA is a potent allergen, and is a frequent cause of allergic contact dermatitis (ACD). MATERIAL AND METHOD: A study was conducted on the results of 726 consecutive children who had been patch tested in the University General Hospital Consortium of Valencia between 1980 and 2015. RESULTS: Almost half (49.7%; (361 cases) of the children had one or more positive patch test findings, with 4.7% (34) being allergic to PPDA. Mean age of patients allergic to PPDA was 12.4 years, and 44.2% were male. There were 2 cases (5.9%) of atopic dermatitis. Of the positive reactions, 73.5% were considered to be current clinically relevant. The sensitisation origin was a Henna tattoo in 50% of cases. CONCLUSION: PPDA sensitisation is relatively common in the child and adolescent population. The most frequent origin is the performing of Henna tattoos adulterated with PPDA. Adolescents are at the higher risk of developing ACD due to Henna tattoos. Henna tattooing should be strongly discouraged in children.

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