Guinea Pig Maximization Test Research Articles

Allergenicity Evaluation of N-(1-Methylheptyl)-N'-Phenyl-p-Phenylenediamine and 2-(Thiocyanomethylthio) Benzothiazole by the Guinea Pig Maximization Test.

In order to regulate contact sensitizers in commercial products, not only is identification of chemical allergens essential but also quantitative evaluation of their allergenicity. We have so far reported threshold values of chemical allergens for both induction and challenge phases in the modified guinea pig maximization test (GPMT). In this study, we examined N-(1-methylheptyl)-N′-phenyl-p-phenylenediamine (MHPPD), an antioxidant for rubber products, and 2-(thiocyanomethylthio) benzothiazole (TCMTB), a biocide for plastic and wood products. MHPPD and TCMTB exhibited distinct profiles of contact allergenicity with the GPMT; that is, both could sensitize guinea pigs by the second induction procedure of topical application alone, even without the first induction procedure of intradermal injection. The calculated challenge threshold values for MHPPD and TCMTB were 0.9 and 0.8 ppm, respectively, which were at least one tenth lower than those of chemical allergens previously examined by us. Octanol-water partition coefficients (log p) used as an index of skin permeability were not necessarily higher for MHPPD and TCMTB than those of other allergens, thus, the skin permeability of these compounds did not seem to be related to their ability to cause sensitization by topical application alone or their low challenge threshold values. The results suggest that the sensitizing potential of both compounds is due to their molecular basis. Cross-reactivities among homologues of both allergens were examined to evaluate their antigenic determinants.

Final Report on the Safety Assessment of Trilaurin, Triarachidin, Tribehenin, Tricaprin, Tricaprylin, Trierucin, Triheptanoin, Triheptylundecanoin, Triisononanoin, Triisopalmitin, Triisostearin, Trilinolein, Trimyristin, Trioctanoin, Triolein, Tripalmitin, Tripalmitolein, Triricinolein, Tristearin, Triundecanoin, Glyceryl Triacetyl Hydroxystearate, Glyceryl Triacetyl Ricinoleate, and Glyceryl Stearate Diacetate

Triesters of glycerin and aliphatic acids, known generically as glyceryl triesters and specifically as Trilaurin, etc., are used in cosmetic products as occlusive skin-conditioning agents and/or non-aqueous viscosity-increasing agents. Hundreds of glyceryl triesters are used in a wide variety of cosmetic products at concentrations ranging from a few tenths of a percent to 46%. Glyceryl triesters are also known as triglycerides; ingested triglycerides are metabolized to monoglycerides, free fatty acids, and glycerol, all of which are absorbed in the intestinal mucosa and undergo further metabolism. Dermal absorption of Triolein in mice was nil; the oil remained at the application site. Only slight absorption was seen in guinea pig skin. Tricaprylin and other glyceryl triesters have been shown to increase the skin penetration of drugs. Little or no acute, subchronic, or chronic oral toxicity was seen in animal studies unless levels approached a significant percentage of caloric intake. Subcutaneous injections of Tricaprylin in rats over a period of 5 weeks caused a granulomatous reaction characterized by oil deposits surrounded by macrophages. Dermal application was not associated with significant irritation in rabbit skin. Ocular exposures were, at most, mildly irritating to rabbit eyes. No evidence of sensitization or photosensitization was seen in a guinea pig maximization test. Most of the genotoxicity test systems were negative. Tricaprylin, Trioctanoin, and Triolein have historically been used as vehicles in carcinogenicity testing of other chemicals. In one study, subcutaneous injection of Tricaprylin in newborn mice produced more tumors in lymphoid tissue than were seen in untreated animals, whereas neither subcutaneous or intraperitoneal injection in 4-to 6-week-old female mice produced any tumors in another study. Trioctanoin injected subcutaneously in hamsters produced no tumors. Trioctanoin injected intraperitoneally in pregnant rats was associated with an increase in mammary tumors in the offspring compared to that seen in offspring of untreated animals, but similar studies in pregnant hamsters and rabbits showed no tumors in the offspring. One study of Triolein injected subcutaneously in rats showed no tumors at the injection site. As part of an effort to evaluate vehicles used in carcinogenicity studies, the National Toxicology Program conducted a 2-year carcinogenicity study in rats given Tricaprylin by gavage. This treatment was associated with a statistically significant dose-related increase in pancreatic acinar cell hyperplasia and adenoma, but there were no acinar carcinomas, the incidence of mononuclear leukemia was less, and nephropathy findings were reduced, all compared to corn oil controls. Overall, the study concluded that Tricaprylin did not offer significant advantages over corn oil as vehicles in carcinogenicity studies. Trilaurin was found to inhibit the formation of neoplasms initiated by dimethylbenzanthracene (DMBA) and promoted by croton oil. Tricaprylin was not teratogenic in mice or rats, but some reproductive effects were seen in rabbits. A low level of fetal eye abnormalities and a small percentage of abnormal sperm were reported in mice injected with Trioctanoin as a vehicle control. Clinical tests of Trilaurin at 36.3% in a commercial product applied to the skin produced no irritation reactions. Trilaurin, Tristearin, and Tribehenin at 40%, 1.68%, and 0.38%, respectively, in commercial products were also negative in repeated-insult patch tests. Tristearin at 0.32% in a commercial product induced transient, mild to moderate, ocular irritation after instillation into the eyes of human subjects. Based on the enhancement of penetration of other chemicals by skin treatment with glyceryl triesters, it is recommended that care be exercised in using them in cosmetic products. On the basis of the available data, the following 23 glyceryl triesters are considered safe as used in cosmetics: Trilaurin, Triarachidin, Tribehenin, Tricaprin, Tricaprylin, Trierucin, Triheptanoin, Triheptylundecanoin, Triisononanoin, Triisopalmitin, Triisostearin, Trilinolein, Trimyristin, Trioctanoin, Triolein, Tripalmitin, Tripalmitolein, Triricinolein, Tristearin, Triundecanoin, Glyceryl Triacetyl Hydroxystearate, Glyceryl Triacetyl Ricinoleate, and Glyceryl Stearate Diacetate. Some of these are not currently in use, but would be considered safe if used at concentrations similar to those glyceryl triesters that are in use as cosmetic ingredients.

歯科用ユージノール製剤によるアレルギー性接触皮膚炎発症の可能性

Eugenol is a main ingredient of clove oil, and either eugenol or clove oil is important constituent in various dental preparations. Rather strong allergenicity of eugenol was confirmed in examination with two methods of modified guinea pig maximization test, which is called adjuvant and patch test, and ear swelling test in mice. Possibility that delayed contact hypersensitivity is induced by use of an eugenol preparation must be admitted. It is found that eugenol in various dental preparations is applied to contact with gingiva or teeth in an enough concentration to cause hypersensitivity especially in the case of some zinc oxide-eugenol preparations such as periodontal dressings and root canal cements. On the other hand clove oil and eugenol are more widely and frequently used for cosmetic and food processing than for dental treatment, and there would be many opportunities in man to get hypersensitivity to eugenol. Even in the case of a new patient the correlation between the allergic symptoms and dental treatment will give rise to the supposition that an eugenol preparation is causing the trouble.

Sensitizer contained in heat-decomposed dye.

Recently a new resorbable P(LA/CL) monofilament suture made of L-lactide and epsilon-caprolactone was developed. The sensitization test was carried out using a guinea pig maximization test according to the Japanese Guidelines. As a result of this test, it was revealed that the methanol extract of P(LA/CL) suture contains a skin sensitizer. It was suggested that the D&C Violet No. 2 contained in P(LA/CL) sutures is decomposed during the melt-spinning process and that the decomposed dye induces skin sensitization. To characterize the sensitizer (the decomposed dye) it was separated and collected by HPLC. To determine the molecular formula of the sensitizer, MS, IR, and NMR spectra were obtained. The molecular weight of the sensitizer was estimated as 240 by measuring the MS. Considering the chemical structure of the dye and the molecular weights, it was determined that the sensitizer was 1,4-dihydroxyanthraquinone (quinizarin). The D&C Violet No. 2 contained in P(LA/CL) sutures was decomposed by the melt-spinning procedure to form quinizarin, one type of anthraquinone dye, and the sensitizer was identified to be, indeed, quinizarin. To evaluate the sensitizing potential of quinizarin, we tested skin sensitization using the maximization test method. Quinizarin induced skin sensitization in guinea pigs, and the minimum sensitizing concentration was approximately 100 ppm. The concentration of quinizarin contained in the P(LA/CL) suture was 1-5 ppm, a value that is lower than the minimum sensitizing concentration of quinizarin. This suggests that P(LA/CL) suture has a low risk with regard to contact dermatitis.

Development of an expert system rulebase for the prospective identification of photoallergens

Relationships between the structure and properties of chemicals can be programmed into knowledge-based systems such as DEREK (an acronym for ‘Deductive Estimation of Risk from Existing Knowledge’). The DEREK knowledge-based computer system contains a sub-set of over 50 rules describing chemical substructures (toxophores) responsible for skin sensitization. This rulebase, based originally on Unilever historical in-house guinea pig maximisation test data, is largely complete and is undergoing refinement as the next stage of its development. As part of an ongoing program of validation and testing, the predictive ability of the sensitization rule set was assessed by processing the structures of over 100 chemical substances in the list of contact allergens identified by the BgVV (German Federal Institute for Health Protection of Consumers). The exercise highlighted areas of chemistry where further development of the rulebase was required, either by extension of the scope of existing rules or by generation of new rules where a sound mechanistic rationale for the biological activity could be established. Several chemicals likely to be acting as photoallergens were identified and rules for photoallergenicity were written covering three classes of chemicals. This paper describes work to extend the DEREK rules for photoallergenicity as part of the European Phototox Project.

Sensitizing capacity of 5,5′‐di‐tert‐butyl‐2,2′‐dihydroxy‐(hydroxymethyl)‐dibenzyl ethers in the guinea pig

In patients hypersensitive to p-tert-butylphenol-formaldehyde resin (PTBP-F-R), it is for diagnostic, therapeutic and preventive reasons necessary to know the identity of the primary sensitizing substances, their sensitizing capacities as well as their cross-reaction patterns. We have recently shown that the 2 dimers in PTBP-F-R, 5,5'-di-tert-butyl-2,2'-dihydroxy-3-hydroxymethyl-dibenzyl ether (X) and 5,5'-di-tert-butyl-2,2'-dihydroxy-3,3'-dihydroxymethyl-dibenzyl ether (IX) are contact sensitizers in man. The aim of this study was to investigate the sensitizing capacities of these dimers in PTBP-F-R and potential cross-reacting substances in the guinea pig with the guinea pig maximization test. IX, X, 2,6-dimethylol-p-tert-butylphenol (2,6-MPTBP), 2-methylol-p-tert-butylphenol (2-MPTBP), p-tert-butylcatechol (PTBC), 5,5'-di-tert-butyl-2,2'-dihydroxy-dibenzyl ether (XI) were used as possible cross reacting substances. IX and X were shown to be sensitizers. When compared to the sensitizers in phenol-formaldehyde resin, IX is a strong sensitizer (p= 0.00052) and X a moderate sensitizer (p=0.0053). Animals sensitized to IX showed cross-reactions to X (p=0.010), 2,6-MPTBP (p=0.0011) and PTBC (p=0.0498). Animals sensitized to X showed no cross-reactions to the substances that were tested. The results indicate that IX is a main allergen in PTBP-F-R, with possibly also X.

Experimental study on skin sensitization potencies and cross-reactivities of hair-dye-related chemicals in guinea pigs.

In screening patch testing of hairdressers with occupational contact dermatitis, multiple positive reactions to hair dye-related chemicals, such as p-phenylenediamine (PPD), p-toluenediamine x 2HCl (PTD) and p-aminophenol (PAP), a fabric dye p-aminoazobenzene (PAB), and a tar dye Sudan III, were frequently encountered. To investigate individual skin sensitization potency and the cross-reactivities among above chemicals, a guinea pig maximization test with the above 5 chemicals was performed. In each group, 6 animals were induced with one of the chemicals at 0.1% concentration by intradermal injection and at 1.0% by topical application. The animals were challenged with all 5 chemicals in concentrations of dilution by 10 from 0.1% to 0.001%. Under the conditions of 0.1% challenges, similar sensitization potencies were observed in PPD (6/6), PTD (6/6), PAP (5/6) and PAB (6/6) groups, but no positive reactions were elicited in the Sudan III group. The cross-reactivities to PPD were confirmed in the animals challenged with PTD (6/6), PAP (6/6), PAB (6/6) and Sudan III (3/6). In the PTD-induced group, positive responses to cross-challenges were elicited by PPD (5/6), PAP (3/6), PAB (5/6) and Sudan III (1/6). The cross-reactivities to PAP were observed only with PPD (2/5) and PAB (5/5). PAB-induced animals responded only to PPD (1/6). The results indicate that all these chemicals except Sudan III are strong sensitizers. Their cross-reactivities are different in sensitized conditions, respectively. The cross-reactivities to PPD were higher than those to PTD, PAP and PAB.

Cross-reactivity patterns of cobalt and nickel studied with repeated open applications (ROATs) to the skin of guinea pigs

Background: The relevance of patch-test reactivity to chemicals on cross-challenge is hard to state, but it is generally assumed that the patient might risk a relapse of contact dermatitis when exposed to the cross-reacting compound(s). Objective: To study relevance by using the repeated open application test (ROAT) and applying the inducing allergen cobalt chloride (COCl 2) or nickel sulfate (NiSO 4) as well as the possibly cross-reacting compound (NiSO 4 or COCl 2) topically to guinea pigs. Method: Animals were induced according to the guinea pig maximization test (GPMT) method, patch tested and then treated for 10 days using ROATs. Sensitivity thresholds were determined with serial dilution tests. Results: Guinea pigs induced with COCl 2 reacted in patch testing (100%) and in ROATs to COCl 2 (93%) but not to NiSO 4. Animals induced with NiSO 4 reacted in patch testing to NiSO 4 (100%) but not to COCl 2, and in the ROATs to NiSO 4 (41%) and less to COCl 2. Conclusions: Our results support the assumption that the concomitant patch test reactivity is due to multiple sensitizations rather than cross-reactivity. We previously found that animals induced with palladium chloride (PdCl 2) also reacted to NiSO 4 on patch testing but not in the ROATs, indicating that the results from patch testing might overestimate the risk of a relapse. ROATs in patients with solitary and/or concomitant sensitivity to COCl 2, NiSO 4 or PdCl 2 are desirable.

Sensitizer contained in heat-decomposed dye

Recently a new resorbable P(LA/CL) monofilament suture made of L-lactide and epsilon-caprolactone was developed. The sensitization test was carried out using a guinea pig maximization test according to the Japanese Guidelines. As a result of this test, it was revealed that the methanol extract of P(LA/CL) suture contains a skin sensitizer. It was suggested that the D&C Violet No. 2 contained in P(LA/CL) sutures is decomposed during the melt-spinning process and that the decomposed dye induces skin sensitization. To characterize the sensitizer (the decomposed dye) it was separated and collected by HPLC. To determine the molecular formula of the sensitizer, MS, IR, and NMR spectra were obtained. The molecular weight of the sensitizer was estimated as 240 by measuring the MS. Considering the chemical structure of the dye and the molecular weights, it was determined that the sensitizer was 1,4-dihydroxyanthraquinone (quinizarin). The D&C Violet No. 2 contained in P(LA/CL) sutures was decomposed by the melt-spinning procedure to form quinizarin, one type of anthraquinone dye, and the sensitizer was identified to be, indeed, quinizarin. To evaluate the sensitizing potential of quinizarin, we tested skin sensitization using the maximization test method. Quinizarin induced skin sensitization in guinea pigs, and the minimum sensitizing concentration was approximately 100 ppm. The concentration of quinizarin contained in the P(LA/CL) suture was 1-5 ppm, a value that is lower than the minimum sensitizing concentration of quinizarin. This suggests that P(LA/CL) suture has a low risk with regard to contact dermatitis.

Analysis of contact dermatitis by cytokines 4--Skin sensitization of biphenyl compounds

Clove buds oil is one of very important natural essential oil with a typical spicy note and also known as a source of eugenol. These phenol compounds, which have the strong perfume of clove, are widely used not only as an analgesic and antiseptic agent in dentistry. However, the problem is that the phenol compounds caused sensitization on the skin occasionally. We reported that the skin sensitization by eugenol and its derivatives was detected in the guinea pig maximization test (GPMT) and also confirmed that dehydrodi-eugenol, a biphenyl compound of eugenol, did not show the skin sensitization. To discuss more, we examined the skin sensitization by several phenol compounds and its biphenyl ones. Consequently, we confirmed that the skin sensitization by biphenyl compounds more remarkably decreased than that by phenol compounds (monomer).

Sensitizing potential in mice, guinea pig and man of the preservative Euxyl K 400 and its ingredient methyldibromo glutaronitrile.

The allergenicity of the preservative Euxyl K 400 and its principal allergen methyldibromo glutaronitrile (MDBGN) (1,2-dibromo-2,4-dicyanobutane) was investigated using 3 animal models; in mice, the local lymph node assay (LLNA) and in guinea pigs, the guinea pig maximization test (GPMT) and the cumulative contact enhancement test (CCET) with a dose-response protocol included. Previous attempts to define the sensitization capacity of these chemicals have given conflicting results. For comparison, the frequency and causes of positive patch test reactions to Euxyl K 400 and MDBGN were studied in patients referred to an occupational dermatology clinic. This investigation showed that Euxyl K 400 and MDBGN can give rise to contact allergy in man and that the relevant cases found mainly had similar exposure as non-occupational cases. A contact allergenic potential could be detected for MDBGN in 2 animal models, i.e., the CCET and the LLNA, and also for Euxyl K 400 in the LLNA. However, statistical analysis of the results from the GPMT with MDBGN failed to detect the sensitizing potential of this particular allergen. The results indicate that to be able to detect the allergenic potential of Euxyl K 400 and MDBGN, a predictive test method with multiple topical applications at induction is required. It is therefore important that an investigator is aware of the possibility of using various predictive test models for investigation of potential contact allergens.

Dose-response studies of contact allergens using 3 guinea pigs models.

A multi-dose-response induction protocol for the guinea pig maximization test (GPMT), including a statistical computer program, has earlier been developed to improve the power of predictive tests for identification of contact allergens. This dose-response protocol, with 2 modifications (i.e., increased number of animals in each group and increased number of challenge concentrations) was evaluated in the GPMT, the cumulative contact enhancement test (CCET) and the Freund's complete adjuvant test (FCAT), using potassium dichromate and hydroxycitronellal as model contact allergens. Application of the dose-response protocol on the CCET and the FCAT resulted in either monotone or non-monotone curves with significant dose-response. However, application of the dose-response protocol on the GPMT gave curves with no significant dose-response. The protocol makes it possible to obtain an EC50 value, thus improving the possibility of ranking contact allergens, which is of substantial use for risk assessments. The dose-response protocol could benefit from a few adjustments: a wider span in the induction doses; change to simultaneous increase in intradermal and topical induction doses to obtain a proper dose-response for the GPMT; the addition of further challenge concentrations. In addition the computer program should allow calculation of threshold concentration for sensitization and EC50 value for a non-monotone curve.

Cross-reactivity patterns of palladium and nickel studied by repeated open applications (ROATs) to the skin of guinea pigs.

Cross-reactivity is usually studied with patch test techniques, but the relevance of a single 1-2 day exposure under occlusion can be questioned. To study relevance, animals were induced with PdCl2 or NiSO4 according to the guinea pig maximization test method and then treated for 10 days according to the repeated open application test (ROAT) method. Animals induced with PdCl2 reacted in the ROATs to PdCl2 (100%) but rarely to NiSO4. Animals induced with NiSO4 reacted in ROATs to the same degree with NiSO4 and PdCl2 (23-30%). The concordance between pre-ROAT patch test results and ROAT outcome was high for PdCl2 (100%) and low (10-40%) for NiSO4. Patch testing seems to overestimate the risk of skin reactions when guinea pigs sensitive to PdCl2 are treated topically with NiSO4. The finding from patch test studies that animals induced with NiSO4 react only to NiSO4 but not to PdCl2 was not confirmed. Repeated open applications more adequately mimic exposure conditions than does patch testing.

A comparison of statistical approaches to the derivation of EC3 values from local lymph node assay dose responses

Effective risk assessment and management of allergic contact dermatitis require three key factors: adequate hazard identification, measurement of the relative potency of identified hazards and an understanding of the nature, extent and duration of exposure. Suitable methods for hazard identification, such as the murine local lymph node assay (LLNA) and the guinea-pig maximization test, are well established and conditions of human exposure normally can be well anticipated. Thus, the need is for a robust and quantitative method for the estimation of relative skin sensitizing potency. One possible approach is via the analysis of LLNA dose–response data, In the LLNA, contact allergens are defined currently as those chemicals that cause a threefold or greater increase in lymph node cell proliferative activity compared with concurrent vehicle-treated controls. It is possible to estimate the concentration of a sensitizer required to generate a threefold stimulation of proliferation in draining lymph nodes; such a concentration is known as the EC3 value. Using a variety of statistical approaches to derive EC3 values from LLNA dose–response data for 10 chemicals, it has been demonstrated that simple linear interpolation between the values either side of the threefold stimulation index provides a robust assessment of the EC3 value without the need for recourse to more sophisticated statistical techniques. Provided that the appropriate concentrations of test chemical have been selected, EC3 values obtained in this way are reproducible both within and between laboratories and form the basis for examination of the utility of this approach for the estimation of relative skin sensitizing potency.

A comparison of statistical approaches to the derivation of EC3 values from local lymph node assay dose responses

Effective risk assessment and management of allergic contact dermatitis require three key factors: adequate hazard identification, measurement of the relative potency of identified hazards and an understanding of the nature, extent and duration of exposure. Suitable methods for hazard identification, such as the murine local lymph node assay (LLNA) and the guinea-pig maximization test, are well established and conditions of human exposure normally can be well anticipated. Thus, the need is for a robust and quantitative method for the estimation of relative skin sensitizing potency. One possible approach is via the analysis of LLNA dose-response data. In the LLNA, contact allergens are defined currently as those chemicals that cause a threefold or greater increase in lymph node cell proliferative activity compared with concurrent vehicle-treated controls. It is possible to estimate the concentration of a sensitizer required to generate a threefold stimulation of proliferation in draining lymph nodes; such a concentration is known as the EC3 value. Using a variety of statistical approaches to derive EC3 values from LLNA dose-response data for 10 chemicals, it has been demonstrated that simple linear interpolation between the values either side of the threefold stimulation index provides a robust assessment of the EC3 value without the need for recourse to more sophisticated statistical techniques. Provided that the appropriate concentrations of test chemical have been selected, EC3 values obtained in this way are reproducible both within and between laboratories and form the basis for examination of the utility of this approach for the estimation of relative skin sensitizing potency.

Toxicological Studies on Procyanidin B-2 for Extern?al Application as a Hair Growing Agent

Procyanidin B-2 [epicatechin-(4 β→8)-epicatechin] is one of condensed tannin that exists widely in plants. We have reported previously that procyanidin B-2 possesses hair epithelial cell growth-promoting activity and stimulates anagen induction in hair cycle progression. To evaluate the safety of topical procyanidin B-2 as a hair growing agent, we examined the mutagenicity, acute subcutaneous injection, primary irritation, skin sensitization, and eye irritation of this compound. Mutagenicity tests using bacteria showed procyanidin B-2 to be non-mutagenic. Chromosomal aberration tests using CHL cells indicated that procyanidin B-2 caused polyploidy but no structural aberrations. In micronucleus tests for mutagenicity using mice, procyanidin B-2 was negative. Acute subcutaneous injection study using rats revealed no symptoms of significant injury. The lethal dose of procyanidin B-2 is greater than 2000 mg/kg (subcutaneous injection). Primary irritation tests using rabbits indicated that procyanidin B-2 containing preparation shows no primary irritation. In the guinea pig maximization test, there was no evidence of sensitization to procyanidin B-2. In primary ocular irritation tests using rabbits, procyanidin B-2 containing preparation and vehicle showed slight irritation of conjunctivae which is assumed to be caused by ethanol. It is suggested that topical procyanidin B-2 is safe and acceptable from the series of toxicological tests.

Sensitizing potential of acetaldehyde and formaldehyde using a modified cumulative contact enhancement test (CCET).

The contact allergenic activity of acetaldehyde was investigated with a modified cumulative contact enhancement test (CCET) method in guinea pigs. Possible cross-reactivity between acetaldehyde and formaldehyde was also studied. In contrast to the original CCET protocol, we used sham-treated controls and the chemicals were tested with closed epicutaneous application at 1st challenge. The suitability of the method was verified with formaldehyde and the results were comparable with those previously found with the guinea pig maximization test (GPMT). For the 1st time, acetaldehyde was shown to be a contact allergen in predictive tests. No cross-reactivity was observed between acetaldehyde and formaldehyde. Acetaldehyde seems to be a rare sensitizer in man. However, its allergenic activity should be considered, since it might be present as an impurity in ethoxylated surfactants. As the CCET protocol involves topical induction and challenge, we regard the modified version as well suited to evaluation of the contact allergenic potential of chemicals.

Validation and subsequent development of the DEREK skin sensitization rulebase by analysis of the BgVV list of contact allergens.

The DEREK knowledge-based computer system contains a subset of approximately 50 rules describing chemical substructures (toxophores) responsible for skin sensitization. This rulebase, based originally on Unilever historical in-house guinea pig maximization test data, has been subject to extensive validation and is undergoing refinement as the next stage of its development. As part of an ongoing program of validation and testing, the predictive ability of the sensitization rule set has been assessed by processing the structures of the 84 chemical substances in the list of contact allergens issued by the BgVV (German Federal Institute for Health Protection of Consumers). This list of chemicals is important because the biological data for each of the chemicals have been carefully scrutinized and peer reviewed, a key consideration in an area of toxicology in which much unreliable and potentially misleading data have been published. The existing DEREK rulebase for skin sensitization identified toxophores for skin sensitization in the structures of 71 out of the 84 chemicals (85%). The exercise highlighted areas of chemistry where further development of the rulebase was required, either by extension of the scope of existing rules or by generation of new rules where a sound mechanistic rationale for the biological activity could be established. Chemicals likely to be acting as photoallergens were identified, and new rules for photoallergenicity have subsequently been written. At the end of the exercise, the refined rulebase was able to identify toxophores for skin sensitization for 82 of the 84 chemicals in the BgVV list.

Simultaneous p-tert-butylphenol-formaldehyde resin and p-tert-butylcatechol contact allergies in man and sensitizing capacities of p-tert-butylphenol and p-tert-butylcatechol in guinea pigs.

In patients who are hypersensitive to p-tert-butylphenol-formaldehyde resin (PTBP-F-R), it is necessary, for diagnostic, therapeutic, and preventive reasons, to know the identity of the primary sensitizing substances, their sensitizing capacities, and their crossreaction patterns. The aims of this study were to investigate the presence of a simultaneous p-tert-butylcatechol (PTBC) contact allergy in individuals who were hypersensitive to PTBP-F-R, to investigate the sensitizing capacity of PTBC and p-tert-butylphenol (PTBP) in guinea pigs, and to study any crossreaction patterns. In 294 dermatitis patients tested with PTBP-F-R and PTBC, there was a statistically significant over-representation of simultaneous test reactions. Use of the guinea pig maximization test demonstrated that PTBC is a strong sensitizer giving crossreactions to PTBP. PTBP, however, failed to induce sensitization.

Contact allergy to the monomers of p-tert-butylphenol-formaldehyde resin in the guinea pig.

In patients hypersensitive to p-tert-butylphenol-formaldehyde resin (PTBP-F-R), and butylphenol derivatives therein, it is for diagnostic, therapeutic and preventive reasons necessary to know the identity of the primary sensitizing substances, their sensitizing capacities as well as their cross-reaction patterns. The monomers in PTBP-F-R, 2-methylol p-tert-butylphenol (2-MPTBP) and 2,6-dimethylol p-tert-butylphenol (2,6-MPTBP), have been shown to be contact sensitizers in man. The aim of this study was to investigate the sensitizing capacities of the monomers and establish cross-reacting patterns in the guinea pig with the guinea pig maximization test. 2,6-MPTBP was shown to be a strong sensitizer while it was indicated that 2-MPTBP was a sensitizer. Animals sensitized to 2,6-MPTBP showed cross-reactions to 2-MPTBP and p-tert-butylcatechol. No cross-reactions were shown to p-tert-butylphenol, tert-butyl 4-hydroxyanisole (BHA) and 3,5-di-tert-butyl 4-hydroxytoluene (BHT).