January 21, 2020

expert reaction to study looking at sunscreen ingredients and absorption into the blood

A study, published in JAMA, reports on the absorption of chemicals found in sunscreen into the users blood. 

Dr Jérôme Labille, Senior Research Scientist, Aix-Marseille University, France, said:

“This is good quality research which addresses the question of the exposure and finds evidence that the tested UV filters are bioavailable (the substance can pass the skin barrier and be found in blood) under normal usage conditions. It does not address the question of hazards or toxicity. Complementary research focused on this latter point is needed to conclude on any risk.

“I was disappointed that the respective concentrations of active ingredients in the four sunscreens studied are not given in this article. This information may enable the reader to better understand the data obtained. For example, the amount of UV filters remaining on the skin was measured at days 7 and 14. It would have been useful to make this measurement at day 0 as well in order to get the initial concentration on the skin just after the product application, and to compare this value with the concentration in the original product. Both the concentrations measured on the skin and in the blood plasma may be correlated to those in the original product. But this question is not explored.

“Regarding the real world, this work can be put in perspective with the consumers habits of sunscreen use, studied on beaches of the French Mediterranean coasts¹. The six UV filters studied here were found in the sunscreen products consumed on the beach under the following frequency: avobenzone 78%, octocrylene 56%, octisalate 52%, homosalate 31%, octinoxate 17%, oxybenzone 2%. This suggests that the present study does not only reflect the typical sunscreen composition in the USA, it is also relevant for a majority of products found in the EU cosmetic market (apart from oxybenzone).

“Mineral UV filters, TiO2 or ZnO ultrafine particles, are also widely used in sunscreen formulations, but they are not considered in this study. The reason may be that they are not preferred in the US market. Nevertheless, such mineral UV filters could be an interesting alternative to the organic molecules studied here because their particles are less able to pass through the skin barrier than organic molecules. Future researches should focus on the advantage/disadvantage of each type of UV filter.

“The authors point that, whatever the findings presented here, individuals should not refrain from the use of sunscreen, because it is required to protect skin against sun rays’ adverse effects. Nevertheless, I think that consumers should be informed of the scientific knowledge regarding UV filters, in order to be able to choose a product with appropriate criteria. Bioavailabilty (availability of the substance to pass the skin barrier and be found in blood) and hazard (endocrine disruptors, allergens, source of oxidative stress, etc) are two key factors that should be regarded when selecting active ingredients in a product.”

1. Labille et al., STOTEN, 706 (2020) 136010).

Prof Antony Young, Emeritus Professor of Experimental Photobiology, King’s College London, said:

“Overall, there is increasing evidence that sunscreens applied to the skin can enter into the circulation. The problem is that we do not know what the health effects of this are. From limited data there is no evidence that long term sunscreen use has any effect on mortality. This would not be an easy area to research on humans for many reasons, not least of which is that sunscreens contain a cocktail of UVR filters. If used correctly, sunscreens are an excellent way to prevent the short and long term adverse effects of solar UVR. There is no reason for this to change.”

Prof Rob Chilcott, Professor of Toxicology, University of Hertfordshire, said:

“The results of this study confirm previous work which demonstrates that the skin is not a perfect barrier and so absorption of small amounts of chemicals from sunscreens (and indeed other skin care products such as cosmetics) is to be expected. This does not mean that sunscreen products are unsafe to use, but that appropriate safety tests need to be performed by manufacturers.

“It should be emphasised that the health benefits of using sunscreens are well established and far outweigh the risks of not protecting the skin from excessive sun exposure. It is also worth considering that the study was performed under conditions which provided a worst-case scenario in terms of the amount of sunscreen applied to the skin. In reality, the amount of sunscreen applied by users will likely be lower and will be subject to continual loss between each application.”

Prof Sir Colin Berry, Emeritus Professor of Pathology, Queen Mary University of London, said:

“It’s important to note that the FDA guideline levels are determined for continuous exposure of test animals, and not intermittent exposures over limited times as this paper looks at. Exceedance of these levels does not mean there is any risk.

“This seems a lot of skin sensitivity for one population [14 out of 48] and it would be useful to know if they have tested the subjects for sensitivity to any components as if there is irritation then absorption will be increased.

“The benefits of sunscreens are well established.”

‘Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients. A Randomized Clinical Trial.’ by Matta et al. was published in JAMA at 16:00 UK time on Tuesday 21^st January. 

DOI: 10.1001/jama.2019.20747

Declared interests

Dr Jérôme Labille: “I have no conflict of interest.”

Prof Antony Young: “I have had research funds and acted as a consultant for the sunscreen industry.”

Prof Rob Chilcott: “I have no conflict of interest in this matter.”

Prof Colin Berry: “No interests.”