The Cancer Council has warned that tattoos can mask skin cancer and prevent an early diagnosis, and that some tattoo inks may actually contain cancer-causing substances.

There is a common misconception that tattoos can protect the skin from developing cancer, as some people mistakenly believe that the ink acts as a physical shield between skin cells and the sun's damaging UV radiation - similar to clothing or sunscreen.

In reality, tattoo ink does not protect the skin from sun damage. In fact, the ink can cover suspicious moles and make them much harder to see, leading to a delayed diagnosis as the changes that usually indicate skin cancer are not found as easily. A later diagnosis can lead to a worse prognosis for the patient.

“The tattoo pigments in your skin may make it difficult for a doctor to accurately detect cancer, delaying diagnosis of melanoma or skin cancer," Cancer Council NSW Hunter regional manager Shayne Connell said.

Concerns are also being raised about toxic tattoo ink travelling inside the body. A study found that nanoparticles from tattoo ink, including chromium and nickel, can travel inside the body and collect inside the lymph nodes, which are part of the immune system.

While there have been no reported cancer cases directly attributable to tattooing, evidence does show that some tattoo inks contain carcinogens. Hazardous components include barium, copper, mercury, amines and various colourants.

People with tattoos are encouraged to keep a close eye on the skin beneath their tattoos and see their doctor if they notice any new or changing lesions.