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Nine studies assessed the skin sensitisation potential of terpineol multiconstituent and its major isomer alpha-terpineol. Reactions related to skin sensitisation were identified in four studies. One of them (Takenaka) could not be properly evaluated because of the lack of information in the experimental conditions used. Therefore, the results of this study could not be considered with full confidence.

Another study identified a surprisingly high rate of positive reactions (13%). This study suffered from major weaknesses that question the reliability of the results reported.

Then, two other studies of relatively good quality identified very low incidence of positive reactions (0.17 and 0.06% among more than 1000 patients tested) although experimental conditions were favouring the occurrence of positive responses (patients suffering from contact dermatitis, many substances tested simultaneously…).

On the other hand, five studies showed no reaction when terpineol multiconstituent was tested. Two of them were performed with too little cohorts of patients (RIFM studies). However, the other ones were of good quality and conducted with a sufficient number of patients. Although the experimental conditions were “pushed” to observe positive responses (contact dermatitis patients in higher ratio than in general population, high concentrations tested…), no reactions were observed in these studies. Lastly, the negative reactions were obtained in three different methodologies (HRIPT, patch test and Human maximisation test) whereas positive responses were observed in patch test methodology only.

The equivocal positive responses observed in humans need to be confronted to the clear negative results observed in some of the human studies and in animal studies.

Therefore, when taking into account all data available in human and in animal studies, terpineol multiconstituent cannot be considered as a skin sensitiser, in a weight of evidence approach.

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