systematic review and meta-analysis reports.a
“Metal allergy to all three metals was significantly more common in European metalworkers with dermatitis attending patch test clinics as compared to ESSCA [European Surveillance System on Contact Allergies] data, indicating a relationship to occupational exposures,” senior study author Jeanne D. Johansen, MD, professor, department of dermatology and allergy, Copenhagen University Hospital, Hellerup, Denmark, and colleagues at the University of Copenhagen wrote in Contact Dermatitis. “However, confounders could not be accounted for.”
How common is metal allergy in metalworkers?
Occupational hand eczema is known to be common in metalworkers. Touching oils, greases, metals, leather gloves, rubber materials, and metalworking fluids as they repeatedly cut, shape, and process raw metals and minerals derived from ore mining exposes metalworkers to allergens and skin irritants, the authors wrote. But the prevalence of allergy to certain metals has not been well characterized.
So they searched PubMed for full-text studies in English that reported metal allergy prevalence in metalworkers, from the database’s inception through April 2022.
They included studies with absolute numbers or proportions of metal allergy to cobalt, chromium, or nickel, in all metalworkers with suspected allergic contact dermatitis who attended outpatient clinics or who worked at metalworking plants participating in workplace studies.
The researchers performed a random-effects meta-analysis to calculate the pooled prevalence of metal allergy. Because 85%-90% of metalworkers in Denmark are male, they compared the estimates they found with ESSCA data on 13,382 consecutively patch-tested males with dermatitis between 2015 and 2018.
Of the 1,667 records they screened, they analyzed data from 29 that met their inclusion criteria: 22 patient studies and 7 workplace studies involving 5,691 patients overall from 22 studies from Europe, 5 studies from Asia, and 1 from Africa. Regarding European metalworkers, the authors found:
- Pooled proportions of allergy in European metalworkers with dermatitis referred to patch test clinics were 8.2% to cobalt (95% confidence interval, 5.3%-11.7%), 8.0% to chromium (95% CI, 5.1%-11.4%), and 11.0% to nickel (95% CI, 7.3%-15.4%).
- In workplace studies, the pooled proportions of allergy in unselected European metalworkers were 4.9% to cobalt, (95% CI, 2.4%-8.1%), 5.2% to chromium (95% CI, 1.0% - 12.6%), and 7.6% to nickel (95% CI, 3.8%-12.6%).
- By comparison, ESSCA data on metal allergy prevalence showed 3.9% allergic to cobalt (95% CI, 3.6%-4.2%), 4.4% allergic to chromium (95% CI, 4.1%-4.8%), and 6.7% allergic to nickel (95% CI, 6.3%-7.0%).
- Data on sex, age, body piercings, and atopic dermatitis were scant.
Thorough histories, protective regulations and equipment
Providers need to ask their dermatitis patients about current and past occupations and hobbies, and employers need to provide employees with equipment that protects them from exposure, Kelly Tyler, MD, associate professor of dermatology, Ohio State University Wexner Medical Center, Columbus, said in an interview.
“Repeated exposure to an allergen is required for sensitization to develop,” said Dr. Tyler, who was not involved in the study. “Metalworkers, who are continually exposed to metals and metalworking fluids, have a higher risk of allergic contact dermatitis to cobalt, chromium, and nickel.”
“The primary treatment for allergic contact dermatitis is preventing continued exposure to the allergen,” she added. “This study highlights the importance of asking about metal or metalworking fluid in the workplace and of elucidating whether the employer is providing appropriate protective gear.”
To prevent occupational dermatitis, workplaces need to apply regulatory measures and provide their employees with protective equipment, Dr. Tyler advised.
“Body piercings are a common sensitizer in patients with metal allergy, and the prevalence of body piercings among metalworkers was not included in the study,” she noted.
The results of the study may not be generalizable to patients in the United States, she added, because regulations and requirements to provide protective gear here may differ.
“Taking a thorough patient history is crucial when investigating potential causes of dermatitis, especially in patients with suspected allergic contact dermatitis,” Dr. Tyler urged.
Funding and conflict-of-interest details were not provided. Dr. Tyler reported no relevant financial relationships.
A version of this article first appeared on.