Many tattoo artists may ink skin with moles or blemishes even though this can make cancer harder to detect, a recent study suggests.

Just 43 per cent of tattoo artists surveyed for the study said they had received training on how to handle skin with moles, spots or other skin lesions. About 55 per cent of the tattoo artists said they had declined to ink skin with any of these visible abnormalities, but they were more apt to refuse for aesthetic reasons than out of concern for skin cancer, the study found.

"The tattoo artists' approach may vary with how large or raised the mole is, but we know that skin cancer can occur even in relatively small and flat lesions, which should not be inked over," said lead study author Westley Mori, a researcher at the University of Pittsburgh Medical School.

Steering clear of lesions or moles may make it easier for tattoo customers to avoid missing early signs of skin cancer or melanoma, Mori said. "Even if a lesion looks normal now, that could change over time," he said. "Tattooing over the moles or other skin lesions can make tracking its evolution by a dermatologist difficult."

Tattooing over the moles or other skin lesions can make tracking its evolution by a dermatologist difficult

Roughly 21 per cent said they had had "great" knowledge about melanoma and 14 per cent reported "great" knowledge about other skin cancers.

However, just 29 per cent of the tattoo artists said they had refused to tattoo skin with a rash, lesion or spot out of concern for skin cancer. That is the same proportion of artists who said they had identified a spot on a client that might be skin cancer or recommended that a customer see a dermatologist to have a suspicious area of skin checked out.

"Tattoo artists definitely are not trained adequately with respect to different skin lesions- not only skin cancers, but also various infections (such as warts) that can spread during the tattoo process," said Dr. Tina Alster, director of the Washington Institute of Dermatologic Laser Surgery and a researcher at Georgetown University Medical Center in Washington, D.C.

Before getting a tattoo, customers should be encouraged to have a dermatologist check for moles or other abnormalities, especially if they have a family history of melanoma, Alster, who wasn't involved in the study, said.

"The public is unaware that tattoo artists hold business licenses, but no safety licenses," Alster said. "In essence, people getting tattoos are having needles inserted in their skin by practitioners with no medical or safety training."