For several years, triclosan [1], a biocide used in many product categories, including cosmetics, has been suspected of being a factor inducing bacterial resistance.

The European Union’s Scientific Committee on Consumer Safety (SCCS) was asked to assess whether a continued use of triclosan as a preservative in cosmetic products is safe taking into account the new provided documentation of resistance development by certain micro-organisms and cross-resistance.

The SCCS notes that low concentrations of triclosan can trigger the expression of resistance and cross-resistance mechanisms in bacteria in vitro, but that the same phenomenon is more difficult to predict in natural environments. “The few in situ studies investigating long-term triclosan exposure (i.e. at least 6 months) did not indicate changes in the resistance susceptibility in the predominant bacteria selected for monitoring, but the changes in the entire flora were not evaluated. Thus additional in situ information is needed to provide a definitive opinion,” the Committee says.

Considering this apparent discrepancy between in situ information that suggests the absence of induction of bacterial resistance and cross-resistance triggered by triclosan, and in vitro studies describing the mechanistic and genetic aspect of triclosan-resistance in bacteria, the SCCS recommends that additional studies be conducted. “Although triclosan resistance was not observed in situ, this is not sufficient to conclude that there is no risk. Information is still lacking to provide a risk assessment on the use of triclosan in cosmetic products.

The SCCS therefore recommends the prudent use of triclosan, for example in applications where a health benefit can be demonstrated.