A controversial study has suggested that some moisturising creams can increase the risk of skin cancer in people who were heavily exposed to sun as youngsters.
But Australian disease experts say the study, which relied on tests performed only on hairless rats, are inconclusive and unnecessarily alarmist, with no proof they apply to humans.
The US study found that moisturisers containing known irritants like sodium lauryl sulphate or mineral oil seemed to increase the rate of tumours in mice pre-exposed to high levels of UV rays.
A custom-made cream not containing these ingredients did not increase the tumour rate.
Lead researcher Allan Conney, a professor in chemical biology at Rutgers University in New Jersey, said his findings "could help explain the incidence of some types of skin cancer in patients," especially those who have had lots of sun exposure.
But Prof Conney acknowledges the results are only in rats, with the significance on humans still "unknown" and more studies needed.
Australian experts say the research, published today in the Journal of Investigative Dermatology, is premature, unhelpful and even irresponsible.
Graham Mann, a professor of medicine at the University of Sydney, said tests were "highly artificial", making the results "very hard to relate to humans and sun-induced skin cancer".
Professor Rod Sinclair, director of the department of dermatology at St Vincent's Hospital in Melbourne, said the significance in humans was "doubtful".
"Moisturiser use is much greater among women. However, skin cancers, and in particular the type of skin cancers studied in this research, seem to be more common among men," Prof Sinclair said.
But he said ways to reduce skin cancer risk needed to remain firmly on the radar as it was the most common cancer in Australia, and rates are expected to increase by 50 per cent by 2020 as the population ages.
Gavin Greenoak, managing director of the Australian Photobiology Testing Facility at the University of Sydney, was heavily critical of the study, saying the researchers' acknowledgment of the need for more research "is an understatement bordering on irresponsibility".
"The potential for alarmism is high, and therefore this paper invites the highest level of scrutiny, which it does not, in my view, sufficiently bear to warrant publication," Mr Greenoak said.
The Cancer Council Australia has called for more further studies into the issue to better inform the public on the real risk of the cream ingredients.
