Preserving with Methylisothiazolinone

Methylisothiazolinone (MI or MIT), a preservative used in cosmetics and other household products, recently has been in the news. Of course, preservatives are essential in almost all cosmetics to prevent the growth of microorganisms during product use, and sometimes to extend the shelf-life of a product, which of course is in the consumer’s interest. Who would want to buy a product that did not last long enough to use it all?

Discarding unused but unusable products is hardly sustainable, but preservatives are much more important for other reasons. Contaminated products can become unpleasant due to off-odors, unpleasant textures and unsightliness. They may also lose efficacy, since the performance of a product often relies on its integrity. In addition, contaminated products can be unsafe to use, potentially introducing large numbers of pathogenic organisms onto the skin, mouth or near the eyes. It is therefore in the consumer’s interest for product manufacturers to ensure the microbiological stability of cosmetics—and this, in most cases, is through the use of preservatives.

European Cosmetics Regulation No. 1223/2009 defines a preservative as a substance that is exclusively or mainly intended to inhibit the development of microorganisms in the cosmetic product. It also stipulates that cosmetic products on the EU market may only contain the approved preservatives listed in Annex V. To be listed in this annex, safety data must be submitted to the European Commission (EC) to be evaluated by its Scientific Committee for Consumer Safety (SCCS). If the dossier gains a positive opinion from the SCCS, a proposal to amend legislation is drafted by the EC and must then be approved by the Member States before being published in the Official Journal of the European Union as new legislation.

Following an evaluation of all safety data, the SCCS gave such an approval to MI in 2005, allowing its use in all cosmetic types at a maximum level of 0.01% (100 ppm). It has since been adopted by many cosmetic manufacturers for use in cosmetic products; however, dermatologists have reported that in patch testing, a higher number of patients tested positive to MI than might be expected for a preservative, and questioned whether MI should continue to be used. As a result, the EC issued the SCCS a mandate to review the safety of MI based on the information provided by the dermatologists. The SCCS draft opinion was open for comment until Feb. 17, 2014. It recommends that MI should not be used in leave-on cosmetics, and that its use in rinse-off cosmetics should be restricted to 0.0015% (15 ppm).

During this open comment period, discussions took place between Cosmetics Europe and key representatives of the European Society for Contact Dermatitis. The conclusion reached was that the clinical data showed some additional restrictions on the use of MI were warranted, although the experience of industry was that consumer complaints to MI-containing products did not seem excessive. As a consequence and ahead of future possible regulatory changes, Cosmetics Europe also issued a recommendation that MI should not be used in leave-on skin care products, including wet wipes, although it may continue to be used in rinse-off cosmetic products at 0.01% (100 ppm). This recommendation is to be adopted as soon as it is able to be put into practice.

This example demonstrates the importance of remaining alert to and encouraging feedback from the marketplace and other sources rather than relying solely on legislative approval. Through collaboration with clinical dermatologists, the industry has been able to move more rapidly than legislation to reduce consumer exposure to an ingredient which, although valuable, has nevertheless proven to lead to unexpected adverse effects.

Changes to product formulations will take time; meanwhile, individuals allergic to MI should avoid products that include it on their ingredient lists. For the majority of consumers with no genetic tendency for an MI allergy, they may continue to use cosmetics with the knowledge that the products will be microbiologically sound.

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