Essential oils are commonly used fragrance ingredients. The oils themselves are complex mixtures, which may contain varying amounts of naturally occurring contact sensitizers. As part of a dermal sensitization risk assessment, the local lymph node assay (LLNA) was used to evaluate the sensitization potential of 7 essential oils and 3 of their major components. The essential oils tested were clove leaf oil, citronella oil, geranium oil, basil oil, lemon grass oil, litsea cubeba and palmarosa oil. The components of each essential oil were characterized by GC/MS. The individual components tested were eugenol, citral and geraniol. The LLNAs were conducted according to OECD guideline 429. Each fragrance material was tested at five dose levels ranging from 2.5 to 50% w/v in 1:3 ethanol:diethyl phthalate. The Stimulation Index (SI) values were calculated for each dose level, an SI of 3 or more was considered to give a positive response. Linear interpolation of the dose response data from each LLNA was then used to derive an estimated concentration (EC3) required to elicit an SI value of 3. The EC3 value was then taken as a measure of relative potency. Eugenol, geraniol and citral were observed to have SI values greater than 3 and, as such, were considered to be potential sensitizers under the conditions of the test. The EC3 values were calculated to be 5.4%, 6.3% and 11.4%, respectively. Based on EC3 values, the potency of each of these three materials can be classified as weakly sensitizing. Positive responses were observed with lemon grass, litsea cubeba, palmarosa and basil oil. The respective EC3 values and subsequent potency classification for each material are 6.5% (weak), 8.4% (weak), 9.6% (weak), 7.1% (weak) and <2.5% (<=moderate). Citronella and geranium oil were not observed to elicit a positive response. However, a mild dose response and SI values nearing three at the highest dose indicate that a positive response and subsequent EC3 value could be expected at doses 50% classifying each material as extremely weak to non-sensitizing.
Animals; Lymph Nodes/ DRUG EFFECTS; Local Lymph Node Assay; Oils, Volatile/ TOXICITY; Perfume; Risk Assessment; Dose-Response Relationship, Drug