Consumers are today being warned that iPads may contain nickel, one of the most common allergy-inducing metals.
Recent reports in medical journals describe nickel allergies from a variety of personal electronic devices, including laptops and mobile phones.
But it was an Apple iPad that caused an itchy body rash in an 11-year-old boy recently treated at a California hospital, according to a report in Paediatrics.
Nickel rashes are not life-threatening, but they can be very uncomfortable and may require treatment with steroids and antibiotics if the skin eruptions become infected, says Dr Sharon Jacob, a dermatologist at Rady Children's Hospital in San Diego, where the boy was treated.
Dr Jacob, who co-wrote the report, said the young patient had to miss school because of the rash.
The boy discussed in the Paediatrics report had a common skin condition that causes scaly patches, but he developed a different rash all over his body that did not respond to usual treatment.
Skin testing showed he had a nickel allergy, and doctors traced it to an iPad his family had bought in 2010.
Doctors tested the device and detected a chemical found in nickel in the iPad's outside coating.
"He used the iPad daily," Dr Jacob said. He got better after putting it in a protective case, she added.
Whether all iPad models and other Apple devices contain nickel is uncertain.
Apple spokesman Chris Gaither said the company's products "are made from the highest quality materials and meet the same strict standards set for jewellery by both the US Consumer Safety Product Commission and their counterparts in Europe".
"We have found that allergies like the one reported in this case are extremely rare," he said.
Microsoft spokeswoman Ryan Bartholomew declined to comment on whether that company's devices contained nickel.
Amy Storey, a spokeswoman for CTIA-The Wireless Association trade group, said nickel was not widely used in the industry's products' outer coatings because it can block radio frequency signals from reaching the devices. She said she did not know which makers used it.
People with existing nickel allergies are at risk for rashes from nickel-containing devices.
According to an advisory about cellphones on the website of the Nickel Institute, a global association based in Toronto representing nickel producers, the risk arises from contact with nickel-plated outer surfaces "over prolonged periods of time".
"The length of time required to elicit an allergic reaction will vary from five or 10 minutes to never, depending on the sensitivity of the individual," the advisory says.
Nickel rashes also have been traced to other common products including some jewellery, glasses frames and zips.
Dr Jacob said evidence suggested nickel allergies were becoming more common, or increasingly recognised. She cited national data showing that about 25% of children who have skin tests for allergies have nickel allergies, against about 17% a decade ago.
Clare Richardson, spokeswoman for the Nickel Institute, said research shows as many as 17% of women and 3% of men in the general population have nickel allergies.
She noted that the European Union has legislation aimed at limiting the amount of nickel that can be released from products that come in direct and prolonged contact with skin.