On March 4, 2020, the SCCS released its opinion that DHA is safe as a hair coloring ingredient in leave-on applications (non-oxidative) up to a maximum of 6.25%; and safe in self-tanning lotions and face creams up to 10%.
DHA or 1,3-dihydroxy-2-propanone (CAS No. 96- 26-4, EC. No 202-494-5) has reported functions of skin conditioning and tanning. Currently, DHA is not regulated under Cosmetic Regulation (EC) No. 1223/2009.
In 2008, SCCS received a dossier to support the safe use of DHA in cosmetic products. In its corresponding opinion, the group concluded, “based upon the available data, the SCCS is of the opinion that the use of dihydroxyacetone as a self-tanning ingredient in cosmetic formulations up to 10% will not pose a risk to the health of the consumer. . . the SCCS considers the use of dihydroxyacetone as a self-tanning ingredient in spray containers up to 14% will not pose a risk to the health of the consumer.”
With the current submission received in May 2019, the applicant requested the safety assessment of DHA intended to be used as a hair coloring ingredient in leave-on applications up to a maximum concentration of 6.25%. The present conclusion responds to this request.
Toxicological Evaluation Irritation and a Draize skin irritation study (1970) previously indicated that DHA does not appear to cause any severe irritation after 24-hr contact under occlusion even on scraped skin. An analogous eye irritation study suggested that DHA is non-irritating to the eye. Although both studies are outdated, the available raw data supports the conclusion that DHA is neither a skin nor an eye irritant.
A more recent Local Lymph Node Assay (2007) showed DHA to be non-sensitizing to the skin in an in vivo model. Two photo-bacterial reverse mutation assays were presented and confirmed the mutagenic potential of non-radiated DHA in Salmonella typhimurium strains TA100 and TA102. However, exposure of DHA to light did not result in an enhanced mutagenic response.
In another test for dermal/percutaneous absorption, the extent of DHA penetration through dermatomed skin into the receptor fluid amounted to just 11.0 μg/cm² (1.67% of the dose applied) with a mean bioavailable dose amounting to only 47.3 μg/cm² (7.22%) of that applied to the skin. Thus, it was shown that DHA, when tested under predicted use conditions, has a low dermal penetration potential. Considering the current conservative SCCS procedure, a value of 64.6 μg/cm² (47.3 μg/cm² plus SD 17.3 μg/cm²) will be used for the Margin of Safety (MoS) calculation.
The experts unanimously concluded that based on the presented raw data and a weight of evidence approach, there is no reason to consider DHA as an in vivo mutagenic/genotoxic substance. The authors conclude that DHA shows to be noncarcinogenic in the presented study.