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A toxicologic and dermatologic review of damascenone when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of isopropyl cinnamate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of alpha-amylcinnamyl alcohol when used as a fragrance ingredient is presented.

The mouse local lymph node assay (LLNA) has been developed and validated for the identification of chemicals that have the potential to induce skin sensitisation. In common with other predictive test methods the accuracy of the LLNA is not absolute and experience has revealed that a few chemicals, including for instance a minority of skin irritants, may elicit false-positive reactions in the assay. To improve further the performance of the LLNA, and to eliminate or reduce false-positives, there has been interest in an adjunct method in which the ability of chemicals to cause increases in the frequency of B220(+) lymphocytes in skin-draining lymph nodes is measured. Previous studies suggest that the use of B220 analyses aligned with the standard LLNA may serve to distinguish further between contact allergens and skin irritants. In the original predictive model, chemicals were regarded as being skin sensitisers if they were able to induce a 1.25-fold or greater increase in the percentage of B220(+) cells within lymph nodes compared with concurrent vehicle controls. Although this first prediction model has proven useful, in the light of more recent experience, and specifically as a consequence of some variability observed in the frequency of B220(+) lymphocytes in nodes taken from vehicle control-treated animals, it is timely now to reconsider and refine the model. As a result a new prediction model is proposed in which reliance on the use of absolute thresholds is reduced, and in which small changes in control values can be better accommodated.

A toxicologic and dermatologic review of ionone when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of cinnamyl propionate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of gamma-damascone when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of allyl cinnamate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of cinnamyl isovalerate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of trans,trans-delta-damascone when used as a fragrance ingredient is presented.

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Reproductive toxicity was determined to have the most conservative systemic exposure derived NO[A]EL of 230 mg/kg/day. A gavage multigenerational continuous breeding study conducted in rats on a suitable read across analog resulted in a MOE of 12,105 while considering 22.6% absorption from skin contact and 100% from inhalation. A MOE of100 is deemed acceptable.

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Reproductive toxicity was based on the Threshold of Toxicological Concern (TTC) of 0.03 mg/kg/day for a Cramer Class I material. The estimated systemic exposure is determined to be equal to this value while assuming 100% absorption from skin contact and inhalation. A systemic exposure at or below the TTC value is acceptable.

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Repeated dose toxicity was determined to have the most conservative systemic exposure derived NO[A]EL of 15 mg/kg/day. A gavage 13-week subchronic toxicity study conducted in rats on a suitable read across analog resulted in a MOE of 10,714 while assuming 100% absorption from skin contact and inhalation. A MOE of >100 is deemed acceptable.

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential as well as environmental safety. Repeated dose, developmental, and reproductive toxicities were determined to have the most conservative systemic exposure derived NO[A]EL of 50 mg/kg/day, based on OECD gavage toxicity studies in rats, that resulted in a MOE of 4545455 after considering 100% absorption from skin contact and inhalation. A MOE of >100 is deemed acceptable.

Rifm fragrance ingredient safety assessment, Benzyl acetate, CAS Registry Number 140-11-4 A.M. Api a, , D. Belsito , S. Bhatia , M. Bruze , P. Calow , M.L. Dagli , W. Dekant , A.D. Fryer , L. Kromidas , S. La Cava , J.F. Lalko , A. Lapczynski , D.C. Liebler , Y. Miyachi , V.T. Politano , G. Ritacco , D. Salvito , T.W. Schultz , J. Shen , I.G. Sipes , B. Wall , D.K. Wilcox a a Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake NJ 07677, USA b Member RIFM Expert Panel, Columbia University Medical Center, Department of Dermatology, 161 Fort Washington Ave., New York, NY 10032, USA c Member RIFM Expert Panel, Malmo University Hospital, Department of Occupational & Environmental Dermatology, Sodra Forstadsgatan 101, Entrance 47, Malmo SE-20502, Sweden d Member RIFM Expert Panel, University of Nebraska Lincoln, 230 Whittier Research Center, Lincoln NE 68583-0857, USA e Member RIFM Expert Panel, University of Sao Paulo, School of Veterinary Medicine and Animal Science, Department of Pathology, Av. Prof. dr. Orlando Marques de Paiva, 87, Sao Paulo, CEP 05508-900, Brazil f Member RIFM Expert Panel, University of Wuerzburg, Department of Toxicology, Versbacher Str. 9, 97078 Wurzburg, Germany g Member RIFM Expert Panel, Oregon Health Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239, USA h Member RIFM Expert Panel, Vanderbilt University School of Medicine, Department of Biochemistry, Center in Molecular Toxicology, 638 Robinson Research Building, 2200 Pierce Avenue, Nashville, TN 37232-0146, USA i Member RIFM Expert Panel, Department of Dermatology, Kyoto University Graduate School of Medicine, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 6068507, Japan j Member RIFM Expert Panel, The University of Tennessee, College of Veterinary Medicine, Department of Comparative Medicine, 2407 River Dr., Knoxville, TN 37996-4500, USA k Member RIFM Expert Panel, Department of Pharmacology, University of Arizona, College of Medicine, 1501 North Campbell Avenue, P.O. Box 245050, Tucson, AZ 85724-5050, USA

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential as well as environmental safety. Repeated dose toxicity was determined to have the most conservative systemic exposure derived NOAEL of 15 mg/kg/day based on a gavage 13-week subchronic toxicity study conducted in rats on a read across analog resulting in a MOE of 1000 considering 100% absorption from skin contact and inhalation. A MOE of >100 is deemed acceptable.

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Repeated dose toxicity was determined to have the most conservative systemic exposure derived NO[A]EL of 29.9 mg/kg/day. A dietary 14-week subchronic toxicity study conducted in rats on a suitable read across analog resulted in a MOE of 3784810 while considering 9.54% absorption from skin contact and 100% from inhalation. A MOE of > 100 is deemed acceptable.

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Repeated dose toxicity was determined using to have the most conservative systemic exposure derived NOAEL of 47 mg/kg/day. A dietary 13-week subchronic toxicity study conducted in rats on a suitable read across analog resulted in a MOE of 2350 while considering 10.3% absorption from skin contact and 100% from inhalation. A MOE of100 is deemed acceptable.

a Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ 07677 USA b Member RIFM Expert Panel, Department of Dermatology, Columbia University Medical Center, 161 Fort Washington Ave., New York, NY 10032, USA c Member RIFM Expert Panel, Department of Occupational & Environmental Dermatology, Malmo University Hospital, Sodra Forstadsgatan 101, Entrance 47, Malmo SE-20502, Sweden d Member RIFM Expert Panel, University of Nebraska Lincoln, 230 Whittier Research Center, Lincoln, NE 68583-0857 USA e Member RIFM Expert Panel, School of Veterinary Medicine and Animal Science, Department of Pathology, University of Sao Paulo, Av. Prof. dr. Orlando Marques de Paiva, 87, Sao Paulo CEP 05508-900, Brazil f Member RIFM Expert Panel, Department of Toxicology, University of Wuerzburg, Versbacher Str. 9, Wurzburg 97078, Germany g Member RIFM Expert Panel, Oregon Health Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239 USA h Member RIFM Expert Panel, Department of Biochemistry, Center in Molecular Toxicology, Vanderbilt University School of Medicine, 638 Robinson Research Building, 2200 Pierce Avenue, Nashville, TN 37232-0146, USA i Member RIFM Expert Panel, Department of Dermatology, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 6068507, Japan j Member RIFM Expert Panel, College of Veterinary Medicine, Department of Comparative Medicine, The University of Tennessee, 2407 River Dr., Knoxville, TN 37996-4500, USA k Member RIFM Expert Panel, Department of Pharmacology, College of Medicine, University of Arizona, 1501 North Campbell Avenue, P.O. Box 245050, Tucson, AZ 85724-5050, USA

a Research Institute for Fragrance Materials, Inc., 50 Tice Boulevard, Woodcliff Lake, NJ 07677, USA b Columbia University Medical Center, Department of Dermatology, 161 Fort Washington Ave., New York, NY 10032, USA c Malmo University Hospital, Department of Occupational & Environmental Dermatology, Sodra Forstadsgatan 101, Entrance 47, Malmo SE-20502, Sweden d University of Nebraska Lincoln, 230 Whittier Research Center, Lincoln, NE 68583-0857, USA e University of Sao Paulo, School of Veterinary Medicine and Animal Science, Department of Pathology, Av. Prof. dr. Orlando Marques de Paiva, 87, Sao Paulo CEP 05508-900, Brazil f University of Wuerzburg, Department of Toxicology, Versbacher Str. 9, 97078 Wurzburg, Germany g Oregon Health Science University, 3181 SW Sam Jackson Park Rd., Portland, OR 97239, USA h Vanderbilt University School of Medicine, Department of Biochemistry, Center in Molecular Toxicology, 638 Robinson Research Building, 2200 Pierce Avenue, Nashville, TN 37232-0146, USA i The University of Tennessee, College of Veterinary Medicine, Department of Comparative Medicine, 2407 River Dr., Knoxville, TN 37996-4500, USA j Department of Pharmacology, University of Arizona, College of Medicine, 1501 North Campbell Avenue, P.O. Box 245050, Tucson, AZ 85724-5050, USA

The use of this material under current use conditions is supported by the existing information. This material was evaluated for genotoxicity, repeated dose toxicity, developmental toxicity, reproductive toxicity, local respiratory toxicity, phototoxicity, skin sensitization potential, as well as, environmental safety. Reproductive toxicity was based on the Threshold of Toxicological Concern (TTC) of 0.03 mg/kg/day for a Cramer Class I material. The estimated systemic exposure is determined to be below this value while assuming 80% absorption from skin contact and 100% from inhalation. A systemic exposure below the TTC value is acceptable.

Allyl esters, frequently used in the fragrance industry, often contain a certain percentage of free allyl alcohol. Allyl alcohol is known to have a potential for delayed skin irritation. Also present in the finished product are different solvent systems, or vehicles, which are used to deliver the fragrances based upon their intended application. This study was conducted to determine whether different vehicles affect the skin irritation potential of five different allyl esters. The allyl esters tested were allyl amyl glycolate, allyl caproate, allyl (cyclohexyloxy)acetate, allyl cyclohexylpropionate, and allyl phenoxyacetate in the vehicles diethyl phthalate, 3:1 diethyl phthalate:ethanol, and 1:3 diethyl phthalate:ethanol at concentrations of 0.1%, 0.5%, 1.0%, and 2.0% ( w/w). A modified cumulative irritation test was conducted in 129 human subjects. Test materials (0.3 ml) were applied under occlusion to skin sites on the back for 1 day (24 h) using Hill Top chambers. Irritation was assessed at 1, 2, 4, and 5 days following application of test materials. Cumulative irritation scores varied considerably among test materials. There were no delayed irritation observations. The highest irritation scores were observed at the 2.0% concentration for all test materials. The irritation scores for allyl amyl glycolate, allyl (cyclohexyloxy)acetate, and allyl phenoxyacetate were highest in 1:3 diethyl phthalate:ethanol, thus the resulting calculated no-observed-effect levels, 0.12%, 0.03%, and 0%, respectively, were much lower for this vehicle compared to the diethyl phthalate vehicle, 0.33%, 0.26%, 0.25%, respectively. These data showed a trend for lower concentration thresholds to induce irritation when higher levels of ethanol were used in the vehicle.

Essential oils are commonly used fragrance ingredients. The oils themselves are complex mixtures, which may contain naturally occurring contact sensitizers. The local lymph node assay was used to evaluate the dermal sensitization potential of basil, citronella, clove leaf, geranium, litsea cubeba, lemongrass, and palmarosa oils. Three of the major components--citral, eugenol, and geraniol--were included to investigate any difference in sensitization potential arising from their exposure in a mixture. Each fragrance material was tested at five concentration 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 SIor = 3 was considered a positive response. The estimated concentration (EC3) required to elicit a positive was calculated and taken as a measure of relative potency. The EC3 values and potency classification for basil, clove leaf, litsea cubeba, lemongrass and palmarosa oils were calculated to be2.5% (or = moderate), 7.1% (weak), 8.4% (weak), 6.5% (weak) and 9.6% (weak), respectively. Citronella and geranium oils were negative. The individual components citral, eugenol and geraniol resulted in EC3 values of 6.3%, 5.4% and 11.4%, respectively. In general, the potency of each essential oil did not differ significantly from that observed for its main individual component.

A toxicologic and dermatologic review of cinnamic acid when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of linalyl butyrate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of linalyl benzoate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of linalyl isovalerate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of linalyl phenylacetate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of linalool when used as a fragrance ingredient, is presented.

A toxicologic and dermatologic review of linalyl formate when used a a fragrance ingredient is presented.

The evaluation of chemicals for their skin sensitising potential is an essential step in ensuring the safety of ingredients in consumer products. Similar to the Threshold of Toxicological Concern, the Dermal Sensitisation Threshold (DST) has been demonstrated to provide effective risk assessments for skin sensitisation in cases where human exposure is low. The DST was originally developed based on a Local Lymph Node Assay (LLNA) dataset and applied to chemicals that were not considered to be directly reactive to skin proteins, and unlikely to initiate the first mechanistic steps leading to the induction of sensitisation. Here we have extended the DST concept to protein reactive chemicals. A probabilistic assessment of the original DST dataset was conducted and a threshold of 64 μg/cm(2) was derived. In our accompanying publication, a set of structural chemistry based rules was developed to proactively identify highly reactive and potentially highly potent materials which should be excluded from the DST approach. The DST and rule set were benchmarked against a test set of chemicals with LLNA/human data. It is concluded that by combining the reactive DST with knowledge of chemistry a threshold can be established below which there is no appreciable risk of sensitisation for protein-reactive chemicals.

An essential step in ensuring the toxicological safety of chemicals used in consumer products is the evaluation of their skin sensitising potential. The sensitising potency, coupled with information on exposure levels, can be used in a Quantitative Risk Assessment (QRA) to determine an acceptable level of a given chemical in a given product. Where consumer skin exposure is low, a risk assessment can be conducted using the Dermal Sensitisation Threshold (DST) approach, avoiding the need to determine potency experimentally. Since skin sensitisation involves chemical reaction with skin proteins, the first step in the DST approach is to assess, on the basis of the chemical structure, whether the chemical is expected to be reactive or not. Our accompanying publication describes the probabilistic derivation of a DST of 64 μg/cm(2) for chemicals assessed as reactive. This would protect against 95% of chemicals assessed as reactive, but the remaining 5% would include chemicals with very high potency. Here we discuss the chemical properties and structural features of high potency sensitisers, and derive an approach whereby they can be identified and consequently excluded from application of the DST.

A toxicologic and dermatologic review of cis-3-hexenyl cinnamate when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of iso-methyl-beta-ionone when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of trans-beta-Ionone when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of 4-(1,2-epoxy-2,6,6-trimethylcyclohexyl)-3-buten-2-one when used as a fragrance ingredient is presented.

A toxicologic and dermatologic review of 6-methyl-β-ionone when used as a fragrance ingredient is presented.

Sensitizing chemicals are commonly associated primarily with either skin or respiratory sensitization. In the Direct Peptide Reactivity Assay (DPRA), when compared with skin sensitizers, respiratory allergens have been demonstrated to selectively react with lysine rather than cysteine. The Peroxidase Peptide Reactivity Assay (PPRA) has been developed as a refinement to the DPRA. The PPRA incorporates dose-response analyses, mass spectroscopy for peptide detection and a horseradish peroxidase-hydrogen peroxide enzymatic system, increasing the potential to identify pro-haptens. In the investigations reported here, the PPRA was evaluated to determine whether it provides advantages for the identification of respiratory allergens. Twenty respiratory sensitizers, including five predicted to be pre-/pro-haptens were evaluated. The PPRA performed similarly to the DPRA with respect to identifying inherently reactive respiratory sensitizers. However, three respiratory sensitizers predicted to be pre-/pro-haptens (chlorhexidine, ethylenediamine and piperazine) were non-reactive and the general selectivity of the respiratory allergens for lysine was lost in the PPRA. Overall, the data indicate that the PPRA does not provide an advantage over the DPRA for discriminating allergens as either contact or respiratory sensitizers. Nevertheless, the PPRA provides a number of refinements to the DPRA that allow for an enhanced characterization of reactivity for both classes of chemical allergens.

It is well known that some chemicals are capable of causing allergic diseases of the skin and respiratory tract. Commonly, though not exclusively, chemical allergens are associated with the selective development of skin or respiratory sensitization. The reason for this divergence is unclear, although it is hypothesized that the nature of interactions between the chemical hapten and proteins is influential. The direct peptide reactivity assay (DPRA) has been developed as a screen for the identification of skin-sensitizing chemicals, and here we describe the use of this method to explore whether differences exist between skin and respiratory allergens with respect to their peptide-binding properties. Known skin and respiratory sensitizers were reacted with synthetic peptides containing either lysine (Lys) or cysteine (Cys) for 24 h. The samples were analyzed by HPLC/UV, and the loss of peptide from the reaction mixture was expressed as the percent depletion compared with the control. The potential for preferential reactivity was evaluated by comparing the ratio of Lys to Cys depletion (Lys:Cys ratio). The results demonstrate that the majority of respiratory allergens are reactive in the DPRA, and that in contrast to most skin-sensitizing chemicals, preferentially react with the Lys peptide. These data suggest that skin and respiratory chemical allergens can result in different protein conjugates, which may in turn influence the quality of induced immune responses. Overall, these investigations reveal that the DPRA has considerable potential to be incorporated into tiered testing approaches for the identification and characterization of chemical respiratory allergens.

To establish further a practical quantitative in chemico reactivity assay for screening contact allergens, lysine peptide was incorporated into a liquid chromatography and tandem mass spectrometry-based assay for reactivity assessments of hapten and pre-/pro-hapten chemical sensitizers. Loss of peptide was determined following 24 h coincubation with test chemical using a concentration-response study design. A total of 70 chemicals were tested in discrete reactions with cysteine or lysine peptide, in the presence and absence of horseradish peroxidase-hydrogen peroxide oxidation system. An empirically derived prediction model for discriminating sensitizers from nonsensitizers resulted in an accuracy of 83% for 26 haptens, 19 pre-/pro-haptens, and 25 nonsensitizers. Four sensitizers were shown to selectively react with lysine including two strong/extreme and two weak sensitizers. In addition, seven sensitizers were identified as having higher reactivity toward lysine compared with cysteine. The majority of sensitizing chemicals (27/45) were reactive toward both cysteine and lysine peptides. An estimate of the relative reactivity potency was determined based on the concentration of test chemical that depletes peptide at or above a threshold positive value. Here, we report the use of EC15 as one example to illustrate the use of the model for screening the skin sensitization potential of novel chemicals. Results from this initial assessment highlight the utility of lysine for assessing a chemical's potential to elicit sensitization reactions or induce hypersensitivity. This approach has the potential to qualitatively and quantitatively evaluate an important mechanism in contact allergy for hazard and quantitative risk assessments without animal testing.

A toxicologic and dermatologic review of 3-phenylpropyl cinnamate when used as a fragrance ingredient is presented. 3-Phenylpropyl cinnamate is a member of the fragrance structural group cinnamyl phenylpropyl compounds. The common characteristic structural element of cinnamyl phenylpropyl materials is an aryl substituted primary alcohol/aldehyde/ester. They are simple aromatic compounds with saturated propyl or unsaturated propenyl side chains containing a primary oxygenated functional group which has little toxic potential. 3-Phenyl-1-propyl derivatives participate in the same beta-oxidation pathways as do their parent cinnamic acid derivatives. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for 3-phenylpropyl cinnamate was evaluated then summarized and includes physical properties, acute toxicity, skin irritation and skin sensitization. A safety assessment of all cinnamyl phenylpropyl compounds will be published simultaneously with this document. Please refer to Belsito et al. (2011) for an overall assessment of the safe use of this material and all the cinnamyl phenylpropyl materials in fragrances. Belsito, D., Bickers, D., Bruze, M., Dagli, M.L., Fryer, A., Greim, H., Miyachi, Y., Saurat, J.H., Sipes, I.G., 2011. A toxicologic and dermatologic assessment of cinnamyl phenylpropyl compounds when used as fragrance ingredients.

A toxicologic and dermatologic review of 3-phenyl-1-propanol when used as a fragrance ingredient is presented. 3-Phenyl-1-propanol is a member of the fragrance structural group cinnamyl phenylpropyl compounds. The common characteristic structural element of cinnamyl phenylpropyl materials is an aryl substituted primary alcohol/aldehyde/ester. They are simple aromatic compounds with saturated propyl or unsaturated propenyl side chains containing a primary oxygenated functional group which has little toxic potential. 3-Phenyl-1-propyl derivatives participate in the same beta-oxidation pathways as do their parent cinnamic acid derivatives. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for 3-phenyl-1-propanol was evaluated then summarized and includes physical properties, acute toxicity, skin irritation, skin sensitization, in vitro skin absorption and mutagenicity. A safety assessment of all cinnamyl phenylpropyl compounds will be published simultaneously with this document; please refer to Belsito et al. (2011) for an overall assessment of the safe use of this material and all cinnamyl phenylpropyl materials in fragrances (Belsito, D., Bickers, D., Bruze, M., Dagli, M.L., Fryer, A., Greim, H., Miyachi, Y., Saurat, J.H., Sipes, I.G., 2011. A toxicologic and dermatologic assessment of cinnamyl phenylpropyl compounds when used as fragrance ingredients.).

Allergic diseases of the skin and respiratory tract resulting from exposure to low molecular weight chemicals remain important issues for consumer product development and occupational/environmental health. Widespread opportunities for exposure to chemical allergens require that there are available effective methods for hazard identification and risk assessment. In the search for new tools for hazard identification/characterization there has been interest in developing alternative methods that will reduce, refine or replace the need for animals. One approach that shows promise is based on the measurement of the peptide reactivity of chemicals; the potential to form stable associations with protein/peptide being a key requirement for the induction of sensitization. Recent investigations using these systems have focused primarily on skin sensitizing chemicals. However, there is interest in the possibility of exploiting these same experimental approaches to distinguish between different forms of chemical allergens - as individual materials are primarily associated with one or the other form of sensitization in humans. These investigations may also provide insight into why chemical sensitizers can differ in the form of allergic disease they will preferentially induce. These opportunities are surveyed here against a background of the immunobiology of allergic sensitization and current state-of-the-art approaches to measurement of peptide/protein reactivity.