Effects of chromium supplementation on glycemic control in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: We aimed to investigate the effect of chromium supplementation on glycemic control indices in patients with type 2 diabetes (T2DM). METHODS: Randomized controlled trials examining the effect of chromium supplementation on glycemic control indices and published before February 2020 were detected by searching online databases, including PubMed, Scopus, Embase, Web of sciences and The Cochrane Library, using a combination of suitable keywords. Mean change and standard deviation (SD) of the outcome measures were used to estimate the mean difference between the supplementation group and the control group at follow-up. RESULTS: Twenty-eight studies reported fasting plasma glucose (FPG), insulin, hemoglobin A1C (HbA1C) and homeostatic model assessment for insulin resistance (HOMA-IR) as an outcome measure. Results revealed significant reduction in FPG (weighted mean difference (WMD): -19.00 mg/dl, 95% CI: -36.15, -1.85, P = 0.030; I2: 99.8%, p < 0.001), insulin level (WMD: -12.35 pmol/l, 95% CI: -17.86, -6.83, P < 0.001), HbA1C (WMD: -0.71 %, 95% CI: -1.19, -0.23, P = 0.004) and HOMA-IR (WMD: -1.53, 95% CI: -2.35, -0.72, P < 0.001; I2: 89.9%, p < 0.001) after chromium supplementation. CONCLUSION: The results of the current meta-analysis study might support the use of chromium supplementation for the improvement of glycemic control indices in T2DM patients.

Germinação de Phaseolus aureus contaminados com diferentes fontes de cromo (VI) / Germination of Phaseolus aureus contaminated with different sources of chromium (VI)

O excesso de Cr nas plantas pode provocar inibição no crescimento das plantas, clorose nas folhas, desequilíbrio nutricional e alteração na germinação das sementes, sendo também altamente tóxico para humanos. Objetivou-se avaliar a germinação de sementes de feijão submetidas a diferentes fontes de Cr, em câmara germinadora durante 9 dias. As fontes de Cr utilizadas: cromato de potássio e dicromato de potássio, em 128 subamostras em soluções de concentrações crescentes de Cr (0, 5,10, 20, 45, 90, 200 e 400 mg L-1). Realizou contagem de sementes normais, anormais e mortas. Conclui-se que sementes de feijão submetidas ao dicromato de potássio germinam 47,5% em média, sem efeitos prejudiciais ao seu desenvolvimento, com apenas 0,87% de sementes anormais e 1,6% em média de sementes mortas, ambas com tolerância de até 400 mg L-1.

Cancer mortality and exposure to nickel and chromium compounds in a cohort of Italian electroplaters.

BACKGROUND: Nickel and chromium-VI compounds are carcinogens for lung cancer, although it is still debated if there is an increased risk at low levels of exposure and for other cancers. METHODS: In a cohort of 2991 Italian electroplaters, a proportion of whom were exposed to low levels of nickel and/or chromium, cumulative exposure to their compounds was obtained by multiplying average concentrations of the metals in each electroplating tank by duration of employment in the company. The association of exposure to compounds with mortality was assessed by multivariable Cox models. RESULTS: No cancer site was associated with chromium exposure controlling for nickel, whereas exposure to nickel significantly increased mortality from lung, rectal, and kidney cancers, even after adjusting for exposure to chromium. CONCLUSIONS: Study results suggest that exposure to nickel compounds may increase the risk of lung cancer even below its occupational exposure limit and indicate possible associations with other cancer sites.

Chromium(III), chromium(VI) and cobalt release from leathers produced in Nicaragua.

BACKGROUND: Leather exposure has been associated with chromium (Cr) and cobalt (Co) contact dermatitis. Cr(VI) in leather is now restricted to <3 mg/kg in the EU. Cr(III) is not restricted. OBJECTIVES: To analyse 29 differently coloured Cr-tanned leather samples from two Nicaraguan tanneries, and to compare their release of Cr, Cr(VI) and Co with that of leathers produced in Europe. METHODS: Cr, Cr(VI) and Co were extracted in phosphate buffer for 3 hours at 25°C according to EN ISO 17075. Atomic absorption spectroscopy and spectrophotometry were used for detection of the metals in phosphate buffer. RESULTS: There was no difference in total Cr or Cr(VI) release between European and Nicaraguan leathers. There was no association between Cr(VI) and total Cr release. Co was released primarily from leathers of one tannery. Cr(III) was released in significantly higher amounts than Cr(VI). CONCLUSIONS: Future investigations and regulations should focus on Cr(III) and Co as well as on Cr(VI).

Differential expression of the PAL gene family in rice seedlings exposed to chromium by microarray analysis.

Phenylalanine ammonia-lyase (PAL) is one of the principle enzymes involved in plant's secondary metabolism. Expression of individual isogene from the PAL gene family is variable with species of plants in responses to different stresses. In this study, transcriptome analysis of the PAL gene family in rice seedlings exposed to potassium chromate Cr(VI) or chromium nitrate Cr(III) was conducted using Agilent 44K rice microarray and real-time quantitative RT-PCR. Uptake and accumulation of both Cr species by rice seedlings and their effect on PAL activity were also determined. Three days of Cr exposure led to significant accumulation of Cr in plant tissues, but majority being in roots rather than shoots. Changes of PAL activities in rice tissues were evident from both Cr treatments. Individual isogene from the rice PAL gene family was expressed differentially in response to both Cr variants. Comparing gene expression between two Cr treatments, only osPAL2 and osPAL4 genes were expressed in similar patterns. Also, gene expression pattern was inconsistent in both plant tissues. Results indicated that expression of individual isoform from the rice PAL gene family is tissue, and stimulus specific under different Cr exposure, suggesting their different detoxification strategies for decreasing or eliminating Cr stresses.

Chromium(III) release from chromium-tanned leather elicits allergic contact dermatitis: a use test study.

BACKGROUND: Chromium (Cr) is a common skin sensitizer. The use of Cr(VI) in leather is restricted in the EU, but that of Cr(III) is not. OBJECTIVES: To assess whether prolonged exposure to Cr-tanned leather with mainly Cr(III) release may elicit allergic contact dermatitis in Cr-allergic individuals. METHOD: Ten Cr-allergic subjects and 22 controls were patch tested with serial dilutions of Cr(III) and Cr(VI), and with leather samples. They then conducted a use test with a Cr-tanned and a Cr-free leather bracelet over a period of 3 weeks, for 12 h per day. Cr deposited on the skin from the bracelets was measured in the controls, and the diphenylcarbazide test for Cr(VI) and extraction tests for Cr(III) and Cr(VI) were conducted for the different leathers. RESULTS: Four of 10 Cr-allergic subjects developed positive reactions to the Cr-tanned bracelet within 7-21 days, whereas only 1 of 10 had a positive patch test reaction to this leather. Cr released from the Cr-tanned leather was most probably entirely Cr(III), with a quantifiable amount being deposited on the skin. CONCLUSIONS: This study strongly suggests that prolonged and repeated exposure to Cr-tanned leather with mainly Cr(III) release is capable of eliciting allergic contact dermatitis in Cr-allergic individuals.

Debunking the Myth of Wool Allergy: Reviewing the Evidence for Immune and Non-immune Cutaneous Reactions.

Although wool is commonly believed to cause irritant (non-immune) and hypersensitivity (immune) cutaneous reactions, the evidence basis for this belief and its validity for modern garments have not been critically examined. Publications from the last 100 years, using MEDLINE and Google Scholar, were analysed for evidence that wool causes cutaneous reactions, both immune-mediated (atopic dermatitis exacerbation, contact urticaria, allergic contact dermatitis) and non-immune-mediated (irritant contact dermatitis, itch). Secondary aims of this paper were to examine evidence that lanolin and textile-processing additives (formaldehyde, chromium) cause cutaneous reactions in the context of modern wool-processing techniques. Current evidence does not suggest that wool-fibre is a cutaneous allergen. Furthermore, contact allergy from lanolin, chromium and formaldehyde is highly unlikely with modern wool garments. Cutaneous irritation from wool relates to high fibre diameters (≥ 30-32 µm). Superfine and ultrafine Merino wool do not activate sufficient c-fibres to cause itch, are well tolerated and may benefit eczema management.

Chromium-induced diffuse dermatitis with lymph node involvement resulting from Langerhans cell histiocytosis after metal-on-metal hip resurfacing.

Total hip arthroplasty (THA) is a highly effective surgical treatment for severe joint involvement. However, due to the release of metal ions in the blood, the patients who undergo hip replacement with metal-on-metal (MOM) bearings may develop signs of allergic skin disease. We report a case of a 60-year-old man who had received MOM hip resurfacing 5 years earlier for osteoarthritis. He presented with a 3-year history of diffuse dermatitis that did not respond to antihistamines and corticosteroids and also had elevated serum levels of chromium and cobalt. A patch test revealed chromium-sulfate hypersensitivity. A skin biopsy showed nonspecific perivascular lymphocytic infiltrate associated with histiocytes. A biopsy of an inguinal lymph node demonstrated large aggregates of Langerhans cells, suggesting type IV delayed-type hypersensitivity. The prosthesis was replaced using ceramic-on-ceramic bearings and the dermatitis resolved after 3 months. The lymph nodes decreased in volume and the serum chromium levels normalized within 24 months of revision surgery. The high levels of serum ions associated with the metal debris from MOM-THAs may induce sensitization and type IV hypersensitivity reactions. Replacing the prosthesis using alternative coupling surfaces is the only approach that has the capacity to resolve these symptoms. Physicians who are not familiar with this issue may misdiagnose systemic symptoms and provide inadequate treatment.

Efectos sobre la salud de la exposición laboral al cromo y sus compuestos: revisión sistemática / Effects of occupational exposure to chromium and its compounds: A systematic review

Objetivos: Revisar la literatura científica sobre los problemas de salud derivados de la exposición laboral a cromo y sus compuestos. Método: Revisión sistemática de la literatura científica recogida en las bases de datos MEDLINE (PubMed), EMBASE, Web of Knowledge, Cochrane Library Plus y LILACS hasta enero de 2013. Los términos utilizados, como descriptores y texto libre, fueron: "Chromium", "Chromium Compounds", "Occupational Exposure" y "Occupational Diseases". Se completó la búsqueda con una revisión de la bibliografía de los artículos seleccionados. Resultados: Se recuperaron 227 referencias, de las que se pudieron recuperar a texto completo 22 artículos tras aplicarlos criterios de inclusión y exclusión. De ellos ocho estudios describen alteraciones genéticas, un estudio alteraciones en la reproducción masculina, cuatro alteraciones respiratorias, siete cáncer y dos dermatitis. El agente asociado con mayor frecuencia a los efectos sobre la salud fue el cromo hexavalente. Conclusión: La exposición laboral al cromo y sus derivados se ha asociado con efectos sobre la salud de gravedad diversa, y por ello se deben emplear medidas de seguridad adecuadas en el entorno laboral con el fin de minimizar dicha exposición y por consiguiente disminuir el número de patologías asociadas. Sería recomendable establecer límites de exposición más restrictivos para este agente, basados en criterios de salud (AU)

Objectives: To review the scientific literature on the health effects of exposure to chromium and chromium compounds on workers. Methods: A systematic review of the scientific literature contained in the MEDLINE (via PubMed), EMBASE, Web of Knowledge, Cochrane Library Plus and LILACS databases through January 2013. The terms searched for, both as subject headings and in free text, were: "chromium", "chromium compounds", "occupational exposure" and "occupational diseases". The search was completed through additional review of the bibliographic references included in the selected papers. Results: We recovered 227 references, from which we selected 22 articles after applying inclusion and exclusion criteria. Of these, genetic alterations were examined in eight studies; in one study, alterations in male reproduction; in four studies, respiratory alterations; in seven studies, cancer; and in two studies, dermatitis. Hexavalent chromium was the agent most frequently associated with the described health effects. Conclusions: Occupational exposure to chromium and chromium derivatives is associated with human health effects of varying severity. This is why adequate control measures should be implemented in the workplace to minimize exposure and diminish the number of associated diseases. More restrictive exposure limits for this agent, based on health criteria, should be established in the future (AU)

miR-375 and miR-30d in the effect of chromium-containing Chinese medicine moderating glucose metabolism.

In China, TianMai Xiaoke tablet (TM) is used to treat type 2 diabetes. However, the exact mechanism of TM is not clear. This study is to investigate the effect of TM on glucose metabolism in diabetic rats and to identify whether TM takes a direct action through microRNAs on islet. Rats were divided into control group, diabetic group, low dose of TM group (TML), and high dose of TM group (TMH). Pancreas samples were analyzed using microRNA array and Q-PCR. Eight-week treatment with TM significantly decreased fasting blood glucose. The blood glucose was significantly reduced in TM-treated groups before and after oral glucose administration. Fasting insulin and HOMA-IR were suppressed in TM-treated groups. miR-448, let-7b, miR-540, miR-296, miR-880, miR-200a, miR-500, miR-10b, miR-336, miR-30d, miR-208, let-7e, miR-142-5p, miR-874, miR-375, miR-879, miR-501, and miR-188 were upregulated, while miR-301b, miR-134, and miR-652 were downregulated in TMH group. Through target gene analysis and real-time PCR verification, we found that these miRNAs, especially miR-375 and miR-30d, can stimulate insulin secretion in islet. Our data suggest that TM can improve blood glucose in diabetic rats which involved increasing the expression of miR-375 and miR-30d to activate insulin synthesis in islet.

Chromium: is it essential, pharmacologically relevant, or toxic?

Over fifty years ago, the element chromium (as the trivalent ion) was proposed to be an essential element for mammals with a role in maintaining proper carbohydrate and lipid metabolism. Evidence for an essential role came from dietary studies with rodents, studies on the effects of chromium on subjects on total parenteral nutrition, and studies of the absorption and transport of chromium. Over the next several decades, chromium-containing nutritional supplements became so popular for weight loss and muscle development that sales were second only to calcium among mineral supplements. However, the failure to identify the responsible biomolecules(s) that bind chromium(III) and their mode of action, particularly a postulated species named glucose tolerance factor or GTF, resulted in the status of chromium being questioned in recent years, such that the question of its being essential needs to be formally readdressed. At the same time as chromium(III)'s popularity as a nutritional supplement was growing, concerns over its safety appeared. While chromium has been conclusively shown not to have beneficial effects on body mass or composition and should be removed from the list of essential trace elements, chromium(III) compounds are generally nontoxic and have beneficial pharmacological effects in rodents models of insulin insensitivity, although human studies have not conclusively shown any beneficial effects. Mechanisms have been proposed for these pharmacological effects, but all suffer from a lack of consistent supporting evidence.

El té verde en la quimioprevención in vivo del daño genotóxico inducido por metales cancerígenos (cromo [VI]) / Green tea and its role on chemoprevention in vivo of genotoxic damage induced by carcinogenic metals (Chromium [VI])

Introducción: Debido a sus componentes antioxidantes, al consumo de infusiones de té verde se le ha asociado con efectos benéficos para la salud, ya que sus antioxidantes pueden jugar un papel importante en el riesgo y la patogénesis de algunas enfermedades crónicas, como algunos tipos de cáncer y enfermedades cardiovasculares. A su vez, se ha reportado que compuestos metálicos como los del Cr [VI] son carcinogénicos e inducen daño genotóxico mediante Estrés Oxidante (EOx). De ahí que, es posible que el té verde proteja del daño genotóxico inducido por estos compuestos. Objetivo: Se evaluó el efecto de la administración por vía oral del té verde sobre el daño genotóxico inducido por Cr [VI], mediante la cuantificación de micronúcleos (MN) en eritrocitos policromáticos (EPC). Material y método: Ratones de la cepa CD-1 fueron divididos en forma aleatoria en los siguientes grupos: (i) testigo, (ii) tratados con té verde, (iii) tratados con trióxido de cromo, (iv) tratados con té verde y trióxido de cromo. El té verde se administró por sonda intragástrica cada 12 horas durante dos días (4 dosis de 0,25 ml de infusiones de 1,6 g/7,5 ml) y ad libitum 5,6 ml/día durante 10 días de infusiones de 3,2 g/100 ml, mientras que, el trióxido de cromo se aplicó por vía intraperitoneal (20 mg/kg). Se obtuvieron muestras de sangre de la vena caudal, en las que se evaluó el número de MN en EPC a las 0, 24, 48 y 72 horas después de los tratamientos. Resultados: El grupo tratado con té verde no presentó cambios estadísticamente significativos en los promedios de MN. Por su parte, el grupo al que se le administró el trióxido de cromo mostró incrementos entre 4 y 8 MN, que resultaron estadísticamente significativos al compararlos con el grupo testigo, lo que corroboró el daño genotóxico. Cuando se combinaron los tratamientos del té verde y trióxido de cromo se observó una disminución en las frecuencias de MN del 31 y 62% a las 72 horas, del 20 y 35% a las 48 horas y del 18 y 31% a las 24 horas con los tratamientos intragástricos y ad libitum respectivamente, en comparación con el grupo tratado solo con el trióxido de cromo. Por lo que, el té verde redujo el daño genotóxico inducido por el trióxido de cromo, y la mayor protección se presentó a las 72 horas. Conclusiones: Nuestros hallazgos muestran un efecto protector del té verde contra el daño al material genético inducido por compuestos metálicos como los del Cr [VI], sugiriendo que sus componentes antioxidantes son los que tienen un efecto quimiopreventivo sobre el EOx generado por el Cr [VI] durante su reducción a Cr [III]. El hecho de que la mayor disminución de la frecuencia de MN se observe a las 72 horas y con el tratamiento ad libitum, sugiere que el efecto protector depende de la biodisponibilidad, farmacodinámica y farmacocinética del principio activo del té verde, por lo que la administración del té verde durante tiempos más prolongados antes de la exposición con compuestos de Cr [VI] podría tener un efecto preventivo más consistente (AU)

Background: Consumption of green tea, by its antioxidant properties, has been associated with beneficial health effects, because antioxidant may play a role in the risk and pathogenesis of several chronic diseases, especially cardiovascular disease and cancer. On the other hand, it has been reported that metal compounds such as chromium [VI] are carcinogenic and can induce genotoxic damage through the Oxidative Stress. Therefore, it is possible that green tea has a protective effect against the genotoxic damage induced by this compounds. Objective: To evaluate the effect of oral administration of green tea over the genotoxic damage induced by Cr [VI] by quantification of micronucleus (MN) in polychromatic erythrocytes (EPC). Materials and methods: We use mice of CD-1 strain that were randomly divided into the following groups: (i) control, (ii) treatment with green tea, (iii) treatment with chromium trioxide, (iv) treatment with green tea and chromium trioxide. The green tea was administrated via intragastric tube every 12 hours over two days (4 doses of 0.25 ml infusions 1.6 g/7.5 ml) and ad libitum (5.6 ml/day for 10 days infusions of 3.2 g/100 ml), while chromium trioxide was administrated via intraperitoneal (20 mg/kg). Blood samples were obtained from the caudal vein, the number of MN in EPC was assessed at 0, 24, 48 and 72 hours after the treatments. Results: The group treated with green tea showed no significant statistical changes in the average of MN. On the other hand, the group that was dosed with the chromium trioxide showed an increase between 4 and 8 MN, which was statistically significant when compared with control group, which confirmed the genotoxic damage. When the green tea treatment was administered before the application of chromium trioxide, there was a decrease in MN frequencies of 31 and 62% at 72 hours, 20 and 35% at 48 hours and 18 and 31% at 24 hours with intragastric and ad libitum respectively, compared with the group treated only with chromium trioxide. Hence, green tea reduced the genotoxic damage induced by chromium trioxide, and the highest protection was presented at 72 hours. Conclusions: Our findings support the protective effects of green tea against the damage of genetic material, induced by metal compounds such as chromium [VI], suggesting that its antioxidant compounds are those that have a chemopreventive effect on the EOX generated by the Cr [VI] during its reduction to Cr (III). The fact that the largest decrease in the frequency of MN was observed at 72 hours and ad libitum treatment, suggests that, the protective effect depends on the bioavailability, pharmacodynamics and pharmacokinetics of the active ingredient in green tea, so the administration of green tea for a long period of time before the exposure to Cr [VI] could have a more consistent preventive effect (AU)

The efficacy of chromium as a growth enhancer for mirror carp (Cyprinus carpio L): an integrated study using biochemical, genetic, and histological responses.

A growth trial was conducted on juvenile mirror carp (Cyprinus carpio L.) for 8 weeks to compare the efficacy of three chromium (Cr) compounds (Cr chloride, Cr picolinate, and Cr yeast) at a level 0.5 mg/kg as a potential growth enhancer. In addition, a high level of Cr (2.0 mg/kg) as Cr chloride has also been added in parallel for comparison. All Cr fortified diets at a level 0.5 mg/kg produced superior growth for carp compared to the control group and the group fed the high level of Cr chloride (2.0 mg/kg). Metabolic indicators measured included two of the key liver enzymes (hexokinase, HK) and (glucose-6-phosphate dehydrogenase, G6PD) activity. The results validated the positive effect of Cr at a level 0.5 mg/kg on enzyme activity and carbohydrate utilization producing significantly better growth performance for mirror carp. The study also included measurement of DNA strand breaks in the erythrocytes using the comet assay which revealed significantly (P < 0.05) increased DNA damage in fish fed on high level of Cr chloride (2.0 mg/kg) but the other treatments were not significantly different (P > 0.05) from the control groups. The concentration of Cr in the liver, gut, and whole fish tissues increased with increasing dietary Cr supplementation. Overall, Cr supplementation at a level 0.5 mg/kg from different sources may affect growth performance in carp by activation of some key liver enzymes (HK and G6PD).

Renal impairment caused by chronic occupational chromate exposure.

PURPOSE: To determine the nephritic toxicity of chromate after chronic occupational exposure. METHODS: The environmental contamination was assessed by measuring the chromium (Cr) in 8-h airborne sampler. The integrated level of Cr was determined by Cr concentrations in the whole blood (WB-Cr) and the urine (U-Cr). The renal glomerular and tubule impairment was evaluated by determination of cystatin C (Cys-C) in the serum and microalbumin (mALB), urinary beta(2)-microglobulin (ß(2)M), N-acetyl-beta-D-glucosaminidase (NAG) activity in the urine. RESULTS: The mean occupational exposure time to Cr was 12.86 years with average daily air level of 27.13 µg/m(3) comparing to 0.11 µg/m(3) of the background level. The WB-Cr and U-Cr were 23.49 µg/L and 17.41 µg/g creatinine (Cre), respectively in the chromate-exposed workers comparing to 3.32 µg/L and 1.52 µg/g Cre in the controls. The serum Cys-C and urinary mALB were significantly increased in the chromate-exposed workers. Exposure to Cr seems to induce an enhanced level of urinary NAG activity and ß(2)M concentration. The increased serum Cys-C concentration was positively correlated with the level of serum Cre. The U-Cr was positively correlated to the concentrations of urinary mALB, ß(2)M, and the activity of NAG. CONCLUSIONS: Chronic occupational exposure to chromate causes comprehensive renal impairment though more severity could occur in the tubule than in the glomerular.

Pediatric dosimetry for intrapleural lung injections of (32)P chromic phosphate.

Intracavitary injections of (32)P chromic phosphate are used in the therapy of pleuropulmonary blastoma and pulmonary sarcomas in children. The lung dose, however, has never been calculated despite the potential risk of lung toxicity from treatment. In this work the dosimetry has been calculated in target tissue and lung for pediatric phantoms. Pleural cavities were modeled in the Monte Carlo code MCNP within the pediatric MIRD phantoms. Both the depth-dose curves in the pleural lining and into the lung as well as 3D dose distributions were calculated for either homogeneous or inhomogeneous (32)P activity distributions. Dose-volume histograms for the lung tissue and isodose graphs were generated. The results for the 2D depth-dose curve to the pleural lining and tumor around the pleural cavity correspond well with the point kernel model-based recommendations. With a 2 mm thick pleural lining, one-third of the lung parenchyma volume gets a dose more than 30 Gy (V(30)) for 340 MBq (32)P in a 10 year old. This is close to lung tolerance. Younger children will receive a larger dose to the lung when the lung density remains equal to the adult value; the V(30) relative lung volume for a 5 year old is 35% at an activity of 256 MBq and for a 1 year old 165 MBq yields a V(30) of 43%. At higher densities of the lung tissue V(30) stays below 32%. All activities yield a therapeutic dose of at least 225 Gy in the pleural lining. With a more normal pleural lining thickness (0.5 mm instead of 2 mm) the injected activities will have to be reduced by a factor 5 to obtain tolerable lung doses in pediatric patients. Previous dosimetry recommendations for the adult apply well down to lung surface areas of 400 cm(2). Monte Carlo dosimetry quantitates the three-dimensional dose distribution, providing a better insight into the maximum tolerable activity for this therapy.

Chromated metal products may be hazardous to patients with chromate allergy.

BACKGROUND: Hidden allergen exposure may contribute to persistence and relapse of chromate dermatitis. According to case reports, chromated metal products, such as screws, fittings, etc., may be relevant allergen sources for patients sensitized to chromate. OBJECTIVES: To examine concomitant patch test reactivity to potassium dichromate 0.5% petrolatum (pet.) and three different types of chromated metal rings. PATIENTS/METHODS: Patients with proven or suspected chromate allergy were patch tested with potassium dichromate 0.5% pet. and three different types of chromated metal rings (yellow, olive, and black). Hexavalent chromium Cr(VI) release from the patch tested rings was chemically analysed. RESULTS: Ninety-five patients were tested: 49/95 (52%) reacted to potassium dichromate and 25/95 (26%) reacted to black chromated rings. Reactions to chromated rings exclusively occurred in patients reacting to potassium dichromate. Of 20 patients with a strong reaction to potassium dichromate, 14 reacted to black chromated rings. These were shown to have a high Cr(VI) release. Only two patients reacted to the other chromated rings, which had a very low Cr(VI) release. CONCLUSIONS: Handling chromated metal products must be regarded a hazard to chromate-sensitive patients, in particular those with a strong sensitization.