London, Nov 20 (IANS) Pain relieving, anti-inflammatory 'cold laser' causes increased skin tumour growth, says a new study.

Jan M. Bjordal from Bergen University College, Norway, worked with a team of Brazilian researchers to carry out experiments in the lab and in living organisms.

'High irradiances (radiation) of low-level laser therapy (LLLT) has gained increasing popularity as a treatment for soft tissue injuries and joint conditions,' said Bjordal.

However, there is a shortage of evidence, especially in living organisms, about the effects of LLLT in malignant conditions such as melanoma.

LLLT was pioneered in the 1970s, when it was discovered that light from low-intensity lasers causes cells to proliferate more rapidly, said a Bergen release.

It is marketed as a treatment for hair-loss, pain management, sports medicine and skin care -- among many other things. Home-treatment sets are available online for unsupervised use.

Bjordal and his colleagues applied LLLT to cancer cultures and to mice injected with melanoma cells.

Although the treatment did not cause any significant changes in the cell cultures, direct irradiation of the tumour with high-dose LLLT caused a significant increase in tumour size and considerable alterations, indicating a worsening of the cancer, in the mice.

These findings were published in the open access journal, BMC Cancer.