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..These and other examples are discussed with particular reference to the fabrication of a gold standard dataset that is required for the validation of in vitro alternatives...

..This paper reports information that was presented during the Workshop...

..Thus, proactive use of QRA, used conservatively and in combination with expert judgment, would have limited the problem of ACD to this new preservative that is known to have caused problems on the consumer market...

..In addition to this, the need for performance standards and an agreed 'gold standard' dataset against which to validate both alternatives and new prediction models is discussed...

..These data underscore the need to consider vehicle effects in the context of skin-sensitization risk assessments...

..Previously, a quantitative risk assessment suggested there was no risk of induction of fragrance allergy from minor residues of fragrance chemicals on washed fabrics...

..For individuals who do still develop contact allergy, avoidance of ACD should continue to be a goal, based on raising awareness of skin protection, allergen labelling and other skincare strategies...

..g. 0.01 ng/m(3)) are commonly associated with other types of safe exposure. Consumer limits typically will lie between these values and depend on the actual exposure associated with product use...

..p-Phenylenediamine (PPD) is an important hair dye allergen, but there remains a reasonable suspicion that other hair dye chemicals may also be responsible for a proportion of the clinical burden of hair dye allergy...

..In chemical classes where the LLNA has been shown to be an inappropriate assay other standardised methods (e.g. the Buehler or Magnusson and Kligman guinea pig tests [OECD 406]) should be employed as the first choice assays...

..However, for the very large majority of HRIPTs conducted concerning the risk of skin sensitization, there is neither scientific justification nor any other merit...

..Consequently, it is concluded that there is no scientific justification for removing the option to use a 4-animal version of the LLNA...

..However, its proper use and interpretation are necessary if those consumers most at risk are to have the information necessary to avoid serious adverse reactions to hair dyes...

..In addition, their relevance for the future development and validation of novel in vitro and in silico alternatives is explored...

..Education for healthcare professionals could usefully be enhanced to take this on board...

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..What has to then be addressed is how information from such in vitro assays is integrated, together with data on epidermal bioavailability, to deliver an assessment of the allergen potency...

..These results support further the utility of EC3 determinations in the LLNA as a measure of the relative potency of a contact allergen...

..No data exist on incidence of senitization to PPD resulting from the use of commercial hair dye preparations over a defined time period...

..We suggest that while PPD may act as a prohapten, there is probably a spectrum of antigenic determinants in vivo. BB may be bound or metabolized by keratinocytes before it reacts with Langerhans cells...

..2% to 0.02% in 1998. It was suspected that this would reduce the incidence of patch test positivity in individuals undergoing routine patch testing after approximately 2-3 years (the Dillarstone effect)...

..We compared rates of atopic dermatitis between patients with allergic contact dermatitis arising out of individual fragrance chemicals with known oral/cutaneous exposure against exclusively cutaneous exposure...

..Consistent with this hypothesis it is notable that over 40 years, with the huge increase in atopic disease, there has also been an increase in dietary hapten exposure through processed food, formula milk and oral antibiotic and drug use...

..CONCLUSIONS: Patients with stronger patch test reactions (++, +++) are more likely to have a clear history of reacting to hair dye and are less likely to still be dyeing their hair...

..The variation seen may reflect the different outcomes measured: irritant threshold visually assesses the skin inflammatory response while TEWL measures skin barrier modification...

..It is more commonly observed with the esters rather than the ethers. Isoeugenyl acetate has been proposed as an alternative to isoeugenol, but there is a high degree of concomitant reactivity with isoeugenol...

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..Their close structural similarity makes the occurrence of simultaneous sensitivity within these chemical pairs likely, although at present there are no robust data to support this hypothesis...

..The hypothesis is advanced that the nature and conditions of skin exposure to common haptens may impact on the quality of cutaneous immune responses such that in some circumstances the development atopic disease is favoured...

..How this can be achieved using the LLNA and employed in safety evaluation is discussed in detail, together with practical suggestions for the deployment of such processes in regulatory toxicology...

..The Deductive Estimation of Risk from Existing Knowledge (DEREK) is one such expert system which is described in further detail...

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..They also confirm that CAPB of suitable purity, where levels of both cocamidopropylamine and DMAPA are minimized, is unlikely to trigger reactions in those ostensibly allergic to the material...

..Accordingly, the evaluation of an additional group of similar aldehydes is now underway to assess the robustness of these models, with some emphasis being based on ensuring a wider spread of chemical reactivity...

..0% subjects and to FM in 12.0%. The absence of a significant difference between the fragrance-allergic group and control group is in keeping with a non-immunological basis for the majority of the immediate reactions seen...

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..In addition, it is possible that irritancy alone does not represent a complete surrogate marker for the ability of a chemical to produce danger signals relevant to the induction of skin sensitization...

..These results are of relevance for the general interpretation of patch test data, especially with regard to risk assessment...

..To explore critically the potential merits of this approach, one specific example is examined in detail...

..The relationship of histological reaction to IT could be related to a differential pro-inflammatory cytokine response in subjects. Low IT has been previously associated with a tumour necrosis factor alpha promoter region polymorphism...

..As a result, risk assessment for contact of protein with skin must take into account potential barrier impairment and thus the possibility of both the induction and the elicitation of allergic skin reactions...

..g. acne vulgaris). The existence of safety signals from commensal bacteria, which prevent initiation of these pathways, may provide opportunities for novel therapeutic approaches to the treatment of inflammatory skin diseases...

..Further development of the irritant threshold test could contribute to the identification of non-atopic subjects at risk of occupational skin disease...

..The use of proteomics has identified a number of proteins which could be used as general markers for skin irritation and which may in particular be of value for the development of in vitro predictive models...

..It is concluded that the OECD Guideline as currently written embodies the necessary flexibility to permit conduct of the LLNA in a manner necessary to meet the varying needs of regulatory agencies and toxicologists around the world...

..We propose that the danger signal in ACD is cytokine release from nonimmune skin cells (principally keratinocytes) and that both the antigenic and "danger" signals arises from the hapten...

..Judicious use of this approach for extrapolating EC3 values can provide information on a likely potency classification for use in risk assessment and may avoid the need for repeat animal testing...

..This understanding is necessary if reliable non-animal approaches, including (quantitative) structure-activity relationships (Q)SARs, read-across, and experimental chemistry based models, are to be developed...

..Therefore, at least for this model protein, non-covalent interactions appear not to be a key determinant of allergen potency...

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..It is concluded that a rLLNA with two mice/group would display decreased sensitivity and is inappropriate for use in hazard identification...

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..These data show the importance of adherence to test guidelines and aligns the clinical experience with resorcinol with that obtained in predictive animal methods...

..This article seeks to consider skin sensitization and ACD in holistic fashion, bridging experimental observations with clinical disease and basic mechanisms with practical toxicology...

..However, a detailed evaluation will be necessary to provide reassurance that a reduction in group size would provide adequate sensitivity across a range of skin sensitization potencies...

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..p.m. Then, where consumer products meet this guideline fully, modern quantitative risk assessment shows clearly that elicitation of ACD is highly improbable, and the chance of the induction of sensitization is even lower...

..Consequently, in vitro or in silico alternatives which can identify the significant acute human skin irritants in this group may well represent suitable alternatives to the rabbit...

..It is hoped that this dataset will accelerate the development, evaluation and eventual validation of new approaches to skin-sensitization testing...

..As a consequence, this substance should not normally be regarded as, or classified as, a significant skin sensitizer...

..Knowledge generated from this work is being incorporated into new/improved rules for sensitization in the expert toxicity prediction system, deductive estimation of risk from existing knowledge (DEREK)...

..2 +/- 0.6%. Given that EC3 values for a variety of contact allergens range over several orders of magnitude, these results further endorse the utility of EC3 values as a reliable indicator of human contact allergenic potency...

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..Clinically, clothing pattern dermatitis associated with fragrance allergy is almost never observed, although this could be investigated clinically by exposing sensitized individuals to the relevant fragrance allergen...

..Thus, recommendations can be made concerning how these considerations can be embraced by those responsible for safety evaluation and for the shaping of regulations for skin sensitizing chemicals/formulations...

..Deriving such information is relevant to our understanding of antigen formation in the immunobiology of skin sensitisation and in the development of in vitro protein haptenation assays...

..It is important to document in the literature the outcome of historical studies that were performed to assess the risk of adverse skin effects associated with their use...

..The purpose of this brief review article is to consider the approaches available and to highlight key procedural issues...

..A key perspective is that no predictive test is without limitations; having a good appreciation of these limitations is necessary for making the best use of the information derived from these methods...

..The outcomes from this collaboration demonstrate the importance of updating and refining computer models for the prediction of skin sensitization as new information from experimental and theoretical studies becomes available...

..Elicitation response characteristics to complete permanent hair dye products in paraphenylenediamine (PPD)-allergic volunteers have not previously been explored in detail...

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..Hence, intermittent exposure to lower concentrations of PPD may be equivalent to higher concentration, one-off exposure...

..Results of LLNA studies have been interpreted in the context of historical clinical data on occupational allergic contact dermatitis associated with exposure to MMA...

..Such knowledge can then be used in order that effective and appropriate in vitro/in silico tools for predicting sensitization potential, with a high confidence, can be developed...

..This observation is the basis for the hypothesis concerning cross-reactivity and the effect of simultaneous exposure. The study found that fragrance allergy could be a common problem in patients with eczema on the hands...

..A positive stinging response on the nasolabial fold may not necessarily predict subjective responses to a product when used on other areas of the face...

..06%), Disperse Blue 3 (1.56%) and Disperse Red 11 (2.13%). We interpreted the simultaneous patch test reactions to PPD and DO3 as due either to cross-sensitivity proper, or to metabolic conversion of textile dyes in the skin to PPD...

..This paper provides an overview of each of these areas with an evaluation of the available scientific database to support an uncertainty factor in the range of 1-10 for each area...

..Both possibilities are consistent with what is understood of the chemistry and composition of commercially available linalool...

..Existing data on formaldehyde may conflict with this theory, though this could be explained by allergen specificity. We propose that further work in this area is needed...

..Detailed statistical analysis of the results indicated that the most important factor driving the induction of skin sensitization was the number of exposures...

..An alternative explanation may be the increasing use of permanent hair dyes...

..In addition to accurately identifying skin sensitizers, the LLNA can also provide a reliable measure of relative sensitization potency, information that is pivotal to the successful management of human health risks...

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..Whether such individuals are those who experience problems with skin care products remains to be addressed...

..It is envisaged that the data from such assays will be integrated with outputs from other in vitro assays in the future to give a prediction of the sensitisation potential of novel chemicals...

..Examples are given for substances falling into various potency groups for skin sensitization relating to results from the local lymph node assay, the guinea pig maximization test, the Buehler method and human experience...

..Further risk factors included leg dermatitis and old age. The frequency of sensitization remains low. It is very unlikely that exposure to cosmetics or personal care products may have played a role in the few cases sensitized...