Earlier this year, the Environmental Working Group (EWG) attacked the use of the vitamin A derivative in products destined for exposure to UV radiation, saying that it was photocarcinogenic.
The claims were made in the EWG’s annual sunscreen report, where the environmental group said most sunscreens on the market were either ineffective or dangerous.
‘No convincing evidence...’
In a commentary published in the Journal of the AAD, dermatologists Henry Lim, Steven Wang and Stephen Dusza argue that there is no convincing evidence to suggest that retinyl palmitate in sunscreens causes cancer.
Retinyl palmitate is used in a number of skin care products due to its antioxidant properties, and is often included as an anti photoaging ingredient.
A number of in vitro tests suggest that when the ingredient is exposed to UVA radiation it can result in the generation of oxygen radicals.
However, the dermatologists argue that in sunscreen products when applied to the skin, the retinyl palmitate will be one of a number of antioxidant ingredients fighting against the formation of free radicals.
“If studied on its own – outside of this environment [in combination with other antioxidants when applied to the skin] its antioxidant properties can rapidly be exhausted, allowing the production of oxygen radicals. In these non-human studies retinyl palmitate was the only compound studies – making the biological relevance of these findings to humans unclear,” one of the authors Dr Wang said.
Retinyl Palmitate has been selected by the National Toxicology Program, an interagency programme that evaluates the toxicological profile of chemicals present in every day products, for further investigation.
Within this investigation, which is ongoing, a number of in vivo studies on mice were performed. EWG analyzed the available data back in May and concluded that the presence of retinyl palmitate when exposed to UV radiation could speed up the development of skin tumours and lesions.
While the data has been published, it has not been peer reviewed and official conclusions not yet drawn, and the Personal Care Products Council warned back in May against making assertions based on preliminary data.
Limitations in mouse study
The authors of the recent commentary in the Journal of the AAD, highlight what they feel to be a number of limitations in the mouse studies.
"While mouse models are an accepted model for carcinogensis, there are limitations: thinner epidermis (hence allowing more UV to penetrate) and a marked propensity to develop skin caner," explained one of the study authors Dr Lim.
"As such, data generated from animal models should be taken in context and not in isolation," he told CosmeticsDesign.com USA.
Ideally, Dr Lim said data from animal models should be combined with the decades of clinical experience with this compound.
"The animal study data need to be taken together with the decades of clinical experience using various forms of retinoids in millions of patients around the world; no evidence from this vast clinical experience suggests that retinoids are photocarcinogeic," he said.
The dermatologists also pointed out that selection by the National Toxicology Program does not mean a compound is dangerous or unsafe. Many other ingredients including AHAs and aloe vera are also under investigation, according to the commentary.