Twenty-five years quaternium-15 in the European baseline series: does it deserve its place there?

For allergens to be included in the European baseline series, they should have allergy rates of at least 1%. In several studies quaternium-15 had lower scores. Also, many cases of sensitization are already detected by formaldehyde contact allergy. The aim of this study was to evaluate whether quaternium-15 deserves continued inclusion in the baseline series on the basis of current criteria: 1% positive reactions, common occurrence in the environment, many relevant reactions. We used the literature survey method in this study. Only the United Kingdom has rates consistently over 1%. The mean for all other countries together and for many individual nations is lower than 1%. At least half of the reactions are already detected by formaldehyde sensitivity, which lowers rates for allergy to quaternium-15 per se (i.e. not caused or at least detected by formaldehyde sensitivity) to less than 0.6% for all countries except the United Kingdom. Neither common occurrence in the environment nor a high percentage of relevant reactions has been ascertained. It may well be argued that quaternium-15 does not deserve its place in the European baseline series and could be incorporated in a cosmetic screening series or preservative series instead. In the United Kingdom, routine testing should be continued.