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Combining preservatives can help lower use level and allergy risk

By Katie Bird , 15-Feb-2011

Using preservatives in combination can help reduce the dose needed and therefore the development of contact allergies that may be associated with them.

According to a recent study led by scientists in Denmark, using cosmetic preservatives in combination can help significantly reduce the levels needed for effective preservation of a product.

In particular, the research highlighted that combining a number of preservatives known to be associated with contact allergies with phenoxyethanol, could lower by 8 to 16 fold the concentrations needed when compared to using the preservatives alone.

“In the formulation we tested three allergenic preservatives (Diazolidinyl urea, MCI/MI and MI). All three were a lot more effective when combined with phenoxyethanol compared to the preservatives used alone,” study author Michael Dyrgaard Lundov told CosmeticsDesign-Europe.com.

Reduce contact allergies

Decreasing the concentration of the preservative in the product could help lower the incidence of contact allergy associated with it, Lundov explained.

“Development of contact allergy is dependent on the exposure dose and thereby the concentration. A reduction in the use-concentration could reduce the number of new cases of contact allergy. But it is difficult to give a precise estimation on the exact effect,” he said.

The past ban on the preservatives methyldibromo glutaronitrile (MDBGN resulted in significant reductions in MDBGN allergic patients, according to Lundov, but he said it was unclear how a reduction in concentrations would affect allergies.

In addition, the scientist also highlighted that some of the same preservatives are used in household products, so a reduction or restriction would be more effective if applied across product groups.

While a third of patients involved in a recent study on the prevalence and cause of MI contact allergy had a relevant exposure through a cosmetic product, the allergenic preservatives are also used in household and industrial products, he explained.

“The legislation for household products and particular industrial products are less strict than cosmetic products. The concentrations of preservatives in these types of products are often higher compared to cosmetics so a combined restriction of the preservatives would be preferable,” Lundov added.

Each formulation is different

Although combining the potentially allergenic preservatives with phenoxyethanol generally helped lower the concentrations needed, the researchers did point out that each formulation is different and requires a different preservation system.

A number of challenge tests would therefore be needed in order to investigate the efficiency of potential preservative combinations.

While this is costly for companies, Lundov said it may be necessary as the regulation of available preservatives may change in the future.

“…the number of available preservatives is probably decreasing. Some of the parabens and MCI/MI are currently being re-assessed by the SCCP, and we believe that if MI is not further regulated it will lead to an epidemic, much like the methyldibromo glutaronitrile (MDBGN). And there are not any new alternatives ready, so in the end in might become a necessity to test new preservatives or combinations as alternatives,” he said.

Source: Low-level efficacy of cosmetic preservatives
doi: 10.1111/j.1468-2494.2010.00619.x
International Journal of Cosmetic Science
M. D. Lundov, J.D. Johnasen, C. Zachariae and L. Moesby