If you're planning on getting a tattoo, make sure it's from a professional and not a friend because ink work by amateurs may carry a risk of Hepatitis C, according to a new report.

In an analysis of several dozen past studies, researchers at the U.S. Centers for Disease Control and Prevention (CDC) found that tattoos from non-professionals appear to increase the risk of a possible blood-borne liver infection.

By contrast, there is no evidence that tattoos done by professionals carried such a risk.Hepatitis C remains a major public health problem in the United States with between 75 and 85 per cent of people infected with the disease developing chronic infection that can lead to serious diseases such as cirrhosis and liver cancer.

The illness is passed to people through contact with infected blood. In the United States, there are roughly 18,000 new Hepatitis C infections every year, mostly when people who inject drugs share tainted needles or syringes.

But there are other ways of contracting the disease.

“Tattoos and piercings can transmit hepatitis C and other infections if performed under non-sterile conditions,” Rania Tohme, an epidemiologist at the CDC who led the study, told Reuters Health in an email.

“People should not have tattoos or piercings done by friends or by people who are not trained professionals.”

The findings, published in Clinical Infectious Diseases, are based on a collection of studies that have been made public since 1994.

In general, people who had tattoos by non-professionals faced a hepatitis C risk that was two to four times higher than average.

Prison tattoos are a particular problem, Tohme's team wrote, because tattooing is so common and inmates may have other risk factors for Hepatitis C.

“To this date, there has been no evidence that tattoos and piercings performed in professional parlors in the United States have been implicated in transmission of hepatitis C virus,” Tohme said.

If going to a non-professional, though, there are some precautions that can be taken, Tohme said.

“Disposable piercing needles, tattoo needles and razors are used on one person and then thrown away. Reusing needles or razors is not safe,”