Scientists are warning that tattoo ink may contain chemicals that cause cancer, and have urged the government to introduce laws protecting customers.
According to recent research, nanoparticles from the ink may enter a person's bloodstream, and toxins may then accumalate in the spleen and kidneys, with potentially harmful effects.
The new research backs up studies conducted by scientists in the US and in the Denmark, where tattoo ink was found to contain traces of carcinogenic chemicals, including cobalt and mercury.
Experts want legislators to warn people of the potential dangers of tattoo ink, by providing them with information on the toxins it may contain in the same way as they are warned about the dangers of smoking tobacco or ultraviolet sun-beds.
Desmond Tobin of Bradford University's centre for skin sciences, who conducted the latest research, told the Sunday Times: "I was frankly gobsmacked when I discovered there is no regulation whatsoever of these dyes.
"We need to do more work, but there is no question that these substances can be toxic," he said.
"It takes a long time for the multiple-step nature of cancer to show its face. I don't think we should wait 20 years to see if there is anything wrong with these ingredients."
It is estimated that about 20% of the adult population of the UK have a tattoos, but parlours are currently only subject to inspections from local authorities to check they meet legal hygiene standards.
Research by Jorgen Serup, Copenhagen university hospital's professor of dermatology, found carcinogenic chemicals in 13 of 21 commonly used European tattoo inks. He has called for information on tattoos to be taken when registering cancer patients and also wants warnings introduced.
"Millions of Europeans are now being tattooed with chemical substances of unknown origin," he said.
"People should be given written information about the inks that are used on them. It may be that, like cigarette smoking, they still choose to take the risk but they need to be informed," he told the Sunday Times.
The Tattoo Ink Manufacturers of Europe believe that about 5% of European tattooists use toxic ink, and wants the EU to compel ink makers to conduct risk assessments on their products and make the results public.
Tattooist Louis Molloy, who counts David and Victoria Beckham among her clients, said that the problem stemmed from pigments imported from China.
"I do acknowledge this is a problem and we do need regulation," Molloy said.