Titanium dioxide acts as a UV filter and is present in numerous products, including cosmetics. It has been proven effective for preventing skin cancer and sunburns, but there have always been concerns about its safety. According to current studies, however, the risks are extremely low.
In sunscreens, day creams, lotions and lip care products, titanium dioxide is only found in the form of nanoparticles [1]. These have a size of 1-10 nm and are suspected to penetrate dermal, respiratory and gastrointestinal barriers, spreading and thus posing a potential risk to the consumer. “In most human skin studies, nanotitanium dioxide particles generally remain on the skin surface after application of a sunscreen formulation. Only a small fraction of the nanoparticles penetrate deeper into the stratum corneum, but do not reach the viable cells of the epidermis or dermis,” said Laurence Imhof, MD, Head of the Department of Aesthetic Dermatology and Physical Therapies at the University Hospital Zurich, summarizing the results of a 2019 publication in JEADV [2].
Except for spray products, application is harmless
Two animal studies suggested cutaneous penetration of titanium dioxide particles in nanoform into the stratum granulosum. In humans, there is only one corresponding finding from an in vivo case study, she said. Two subjects applied a commercial sunscreen containing nanotitanium dioxide particles six times daily [3]. Seven days after application, particles beyond the stratum corneum were detected in viable cells of the dermis using a transmission electron microscope. The speaker puts these findings into perspective: “That would mean that you would have to rub in these sunscreens very consistently several times a day, which is not the reality.” In the review by Dreno et al. the conclusion is as follows: Almost all studies conducted on humans or animals to date would have shown that the penetration of nanotitanium dioxide particles was largely limited to the stratum corneum. Except for the one study by Naess et al. the nanotitanium dioxide particles did not enter the skin beyond the surface layers to the viable cells. This was evident in both healthy and damaged skin. However, the authors advise against the use of spray products containing nanotiandioxide because inhaled nanoparticles can diffuse across the lung barrier and translocate to the rest of the body. While human data on this are sparse and inconsistent, he said, there are data from animal studies describing pneumonia. Regarding oral exposures of nanotitanium dioxide particles, for example during the application of lip care products, the authors mention that no adverse health effects are expected, although these particles could potentially penetrate the gastrointestinal mucosa after oral ingestion, but probably only to a limited extent.
Source: ZDFT 2020
Literature:
- Imhof L: What’s new in Aesthetic Dermatology? Laurence Imhof, MD, Zurich Dermatology Continuing Education Days (ZDFT), May 14-15, 2020.
- Dreno B, et al: Safety of titanium dioxide nanoparticles in cosmetics. JEADV 2019; 33 Suppl 7: 34-46.
- Naess EM, et al: Titanium dioxide nanoparticles in sunscreen penetrate the skin into viable layers of the epidermis: a clinical approach. Photodermatol Photoimmunol Photomed 2016; 32: 48-51.
DERMATOLOGIE PRAXIS 2020; 30(5): 22 (published 8/10/20, ahead of print).
