Human Repeated Insult Patch Test Research Articles

FC04.4 Impact of exposure duration on the induction of contact allergy

It has been demonstrated for a wide range of contact allergens that the degree to which sensitisation is induced is highly dependent on the dose per unit area of material applied to the skin. For a given skin area, the concentration of the contact allergen applied may be conveniently expressed as a percentage. However, although a number of other variables affecting induction have been examined, little attention has been paid to the impact of the duration of skin contact. For example, in the human repeated insult patch test the 9 inductions exposures may be applied for either 24h or for a combination of 48h and 72h, the latter ensuring continuous exposure during the 3 week induction period.Under these latter conditions, it is known that the contact allergen p‐phenylenediamine (PPD) sensitises quite efficiently; historical data with 1% PPD in petrolatum resulted in a sensitisation rate of 47/88 (54%). Applying the same dose per unit area, we examined the impact of reducing the exposure time to 9 × 5 minutes spaced over the same 3 week period. Under these conditions, PPD sensitised only 2/102 (2%) of subjects. The data suggest that one route to the limitation of the extent of contact allergy would be to limit the duration of skin exposure.

PCS.04 Establishment of safe exposure limits for the induction of allergy. Theory

For new chemicals introduced into the workplace or marketplace, and which come into contact with the skin, it is necessary, to conduct a thorough skin safety testing and risk assessment program to be certain that the exposures will be well tolerated. One vital risk assessment process involves the determination of allergic skin reactions, referred to as skin sensitization, the clinical manifestation of which is allergic contact dermatitis. The process by which low molecular weight chemicals induce and elicit skin sensitization is dependent on many factors including the ability of the chemical to penetrate the skin, react with protein, and trigger a cell‐mediated immune response. Based on our chemical, cellular and molecular understanding of allergic contact dermatitis, it is possible to carry out a quantitative risk assessment. It has been well known for years that chemical allergens display dose‐response characteristics regardless of whether the sensitization is induced in an experimental system or in humans. Moreover, it is well known that the critical exposure determinant for evaluating skin sensitization risk is dose per unit area of skin exposed. The skin sensitization testing and risk assessment process for new ingredients and consumer products generally follows a step‐wise approach that may involve structure‐activity evaluations, analytical assessments, preclinical skin sensitization testing (e.g., the mouse local lymph node assay), confirmatory clinical testing (e.g., the human repeat insult patch test), and benchmarking of resulting data against similar ingredients and product types. Essential elements for conducting a sound risk assessment involve the development of an understanding of the sensitization potential of the contact allergen and the likely dose, nature, extent and duration of exposure. With an understanding of the exposure and potency of the chemical one can assess whether the chemical, under the specific conditions of exposure, ould pose an acceptable or unacceptable risk of induction of skin sensitization. As with any test method or risk assessment approach, it is critical to understand the strengths and limitations so that one can conduct the best assessment possible and assure the skin safety of the chemical under evaluation.

Final Report of the Amended Safety Assessment of Glyceryl Lau rate, Glyceryl Lau rate SE, Glyceryl Laurate/Oleate, Glyceryl Adipate, Glyceryl Alginate, Glyceryl Arachidate, Glyceryl Arachidonate, Glyceryl Behenate, Glyceryl Caprate, Glyceryl Caprylate, Glyceryl Caprylate/Caprate, Glyceryl Citrate/Lactate/Linoleate/Oleate, Glyceryl Cocoate, Glyceryl Collagenate, Glyceryl Erucate, Glyceryl Hydrogenated Rosinate, Glyceryl Hydrogenated Soyate, Glyceryl Hydroxystearate, Glyceryl Isopalmitate, Glyceryl Isostearate, Glyceryl Isostearate/Myristate, Glyceryl Isostearates, Glyceryl Lanolate, Glyceryl

The safety of 43 glyceryl monoesters listed as cosmetic ingredients was reviewed in a safety assessment completed in 2000. Additional safety test data pertaining to Glyceryl Rosinate and Glyceryl Hydrogenated Rosinate were received and served as the basis for this amended report. Glyceryl monoesters are used mostly as skin-conditioning agents--emollients and/or surfactant--emulsifying agents in cosmetics. The following 20 glyceryl monoesters are currently reported to be used in cosmetics: Glyceryl Laurate, Glyceryl Alginate, Glyceryl Arachidonate, Glyceryl Behenate, Glyceryl Caprylate, Glyceryl Caprylate/Caprate, Glyceryl Cocoate, Glyceryl Erucate, Glyceryl Hydroxystearate, Glyceryl Isostearate, Glyceryl Lanolate, Glyceryl Linoleate, Glyceryl Linolenate, Glyceryl Myristate, Glyceryl Oleate/Elaidate, Glyceryl Palmitate, Glyceryl Polyacrylate, Glyceryl Rosinate, Glyceryl Stearate/Acetate, and Glyceryl Undecylenate. Concentration of use data received from the cosmetics industry in 1999 indicate that Glyceryl Monoesters are used at concentrations up to 12% in cosmetic products. Glyceryl Monoesters are not pure monoesters, but are mostly mixtures with mono-, di-, and tri-esters. The purity of commercial and conventional Monoglyceride (Glyceryl Monoester) is a minimum of 90%. Glyceryl Monoesters (monoglycerides) are metabolized to free fatty acids and glycerol, both of which are available for the resynthesis of triglycerides. Glyceryl Laurate enhanced the penetration of drugs through cadaverous skin and hairless rat skin in vitro and has been described as having a wide spectrum of antimicrobial activity. A low-grade irritant response was observed following inhalation of an aerosol containing 10% Glyceryl Laurate by test animals. Glyceryl monoesters have little acute or short-term toxicity in animals, and no toxicity was noted following chronic administration of a mixture consisting mostly of glyceryl di- and mono- esters. Glyceryl Laurate did have strong hemolytic activity in an in vitro assay using sheep erythrocytes. Glyceryl Laurate, Glyceryl Isostearate, or Glyceryl Citrate/Lactate/Linoleate/Oleate were not classified as ocular irritants in rabbits. Undiluted glyceryl monoesters may produce minor skin irritation, especially in abraded skin, but in general these ingredients are not irritating at concentrations used in cosmetics. Glyceryl monoesters are not sensitizers, except that Glyceryl Rosinate and Hydrogenated Glyceryl Rosinate may contain residual rosin, which can cause allergic reactions. These ingredients are not photosensitizers. Glyceryl Citrate/Lactate/Linoleate/Oleate was not mutagenic in the Ames test system. Glyceryl Laurate exhibited antitumor activity and Glyceryl Stearate was negative in a tumor promotion assay. At concentrations higher than used in cosmetics, Glyceryl Laurate did cause moderate erythema in human repeat-insult patch test (RIPT) studies, but the other glyceryl monoesters tested failed to produce any significant positive reactions. Glyceryl Rosinate was irritating to animal skin at 50%, but did not produce sensitization in clinical tests at concentrations up to 10% and covered with semioccluded patches. There is reported use of Glyceryl Rosinate at 12%in mascara, which is somewhat higher than the concentration in the clinical testing. It was reasoned that the available data do support the safety of this use because there would be minimal contact with the skin and no occlusion. The safety of Arachidonic Acid was not documented and substantiated for cosmetic product use in an earlier safety assessment and those same safety questions apply to Glyceryl Arachidonate. Based on these data, the Cosmetic Ingredient Review (CIR) Expert Panel found that these glyceryl monoesters are safe as cosmetic ingredients in the present practices of use and concentration: except that the available data are insufficient to support the safety of Glyceryl Arachidonate. Additional data needed to support the safety of Glyceryl Arachidonate include (1) dermal absorption data; and, based on the results of the absorption studies, there may be a need for (2) immunomodulatory data; (3) carcinogenicity and photocarcinogenicity data; and (4) human irritation, sensitization, and photosensitization data.

Proposal for a risk assessment methodology for skin sensitization based on sensitization potency data

In this paper, we propose a quantitative risk assessment methodology for skin sensitization aiming at the derivation of ‘safe’ exposure levels for sensitizing chemicals, used e.g., as ingredients in consumer products. Given the limited number of sensitizers tested in human sensitization tests, such as the human repeat-insult patch test (HRIPT) or the human maximization test (HMT), we used EC3 values from the local lymph node assay (LLNA) in mice because they provide the best quantitative measure of the skin sensitizing potency of a chemical. A comparison of LLNA EC3 values with HRIPT and HMT LOEL, and NOEL values was carried out and revealed that the EC3, expressed as area dose, can be used as a surrogate value for the human NOEL in risk assessment. The uncertainty/extrapolation factor approach was used to derive (a) an ‘acceptable non-sensitizing area dose’ (ANSAD) to protect non-allergic individuals against skin sensitization and (b) an ‘acceptable non-eliciting area dose’ (ANEAD) to protect allergic individuals against elicitation of allergic contact dermatitis. For ANSAD derivation, interspecies, intraspecies and time extrapolation factors are applied to the LLNA EC3. For ANEAD derivation, additional application of a variable sensitization–elicitation extrapolation factor is proposed. Values for extrapolation factors are derived and discussed, the proposed methodology is applied to the sensitizers methylchloroisothiazolinone/methylisothiazolinone, cinnamic aldehyde and nickel and results are compared to published risk assessments.

A modified human repeat insult patch test for extended mucosal tissue exposure.

A modified human repeat insult patch test for extended mucosal tissue exposure.

Lack of sensitization for trimellitate, phthalate, terephthalate and isobutyrate plasticizers in a human repeated insult patch test

Two hundred and three human volunteers were tested for evidence of sensitization to several plasticizers following 3 weeks of dermal application three times a week. Tris(2-ethylhexyl)mellitate (TOTM; 1%, v/v), 2,2,4-trimethyl-1,3-pentanediol-diisobutyrate (TXIB; 1%, v/v), di(2-ethylhexyl)terephthalate (DEHT; 0.5%, v/v) and diethylphthalate (DEP; 2%, v/v) were applied to the skin of volunteers under semi-occlusive patch for 3 consecutive weeks and the reactions to a challenge application noted following a 2-week rest period. Slight erythema was observed in four individuals exposed to TOTM, two of which resolved within 96 h and one that occurred only after 96 h. Slight erythema was noted in three subjects exposed to TXIB, one of which resolved by 96 h and one that occurred only after 96 h. Two subjects had slight erythema to DEHT, one that resolved by 96 h and one that occurred only after 96 h. One reaction occurred with DEP at 96 h after challenge. Of the positive responses, one subject reacted to all test substances. No subject had a response grade of 1.0 or greater. Because of the low response, the overall conclusion is that none of the plasticizers demonstrated evidence of sensitization or irritation.

A skin sensitization safety assessment of a new bleach activator technology in detergent applications.

A new chemical called nonanoyl amido caproylacid oxybenzenesulphonate (NACAOBS) is being developed for use as a bleach activator in laundry detergents. Bleach activators, like NACAOBS, are typically used at levels between 2% and 6% in laundry detergents. NACAOBS is stable in aqueous solutions, but undergoes rapid perhydrolysis when combined with water and peroxygen bleach in laundry detergents. Animal testing demonstrated that NACAOBS, as a raw material, is a weak skin sensitizer. Clinical testing, including extended simulated laundry pretreatment, human repeat insult patch testing and home use testing was then undertaken, following sufficient reassurance of 1) the weak sensitization potential of the substance, 2) its rapid degradation in laundry wash solutions and, consequently, 3) low-to-negligible consumer dermal exposures to the native substance. Results confirmed the skin sensitization safety profile of laundry detergents containing NACAOBS, namely the absence of any reaction suggestive of contact sensitization (even under exaggerated dermal exposure conditions in a detergent matrix), and a skin compatibility profile comparable to that of current detergents. Further confirmation of the skin safety profile was obtained from a successful 12-month market test of a granular detergent containing 3.6% of the new substance, during which not a single adverse skin reaction was reported. In addition, NOBS (an oxybenzenesulphonate structural analogue to NACAOBS) has similar toxicological properties and has been safely marketed in detergents at similar levels for many years. It can be concluded that the likelihood of NACAOBS to induce skin sensitization or even elicit allergic reactions in consumer detergent use scenarios is negligible.

Skin sensitization testing in potency and risk assessment.

The purpose of this article is to review, and make recommendations for, the use of relevant skin sensitization test methods, for the purposes of determination of relative potency and the threshold dose necessary for the induction of skin sensitization, and for risk assessment. In addressing the first area, the utility of three guinea pig tests (the guinea pig maximization test, the occluded patch test, and the open epicutaneous test) of the local lymph node assay (LLNA) and of human volunteer testing for the assessment of relative potency and identification of thresholds for sensitization were considered. The following conclusions were drawn. (1) Although attempts have been made to modify the guinea pig maximization test for the purposes of deriving dose-response relationships, this method is usually unsuitable for determination of relative sensitizing potency. (2) Guinea pig methods that do not require the use of adjuvant and which employ a relevant route of exposure (the occluded patch test and the open epicutaneous test) are more appropriate for the assessment of relative skin-sensitizing potency. (3) The LLNA is suitable for the determination of relative skin sensitizing potency, and the adaptation of this method for derivation of comparative criteria such as EC3 values (the estimated concentration of test chemical required to induce a stimulation index of 3 in the LLNA) provides an effective and quantitative basis for such measurements. (4) For all the methods identified above, potency is assessed relative to other chemical allergens of known skin sensitizing potential. The estimation of likely threshold concentrations is dependent upon the availability of suitable benchmark chemicals of known potency for human sensitization. (5) Human testing (and specifically, the Human Repeat Insult Patch Test) can provide information of value in confirming the absence of skin sensitizing activity of formulations and products under specific conditions of use and exposure. Based on the above, the following recommendations are made. (1) If results are already available from suitable guinea pig tests, then judicious interpretation of the data may provide information of value in assessing relative skin sensitizing potency. This option should be explored before other analyses are conducted. (2) The LLNA is the recommended method for new assessments of relative potency, and/or for the investigation of the influence of vehicle or formulation on skin sensitizing potency. (3) Whenever available, human skin sensitization data should be incorporated into an assessment of relative potency. With respect to risk assessment, the conclusion drawn is that all the available data on skin-sensitizing activity in animals and man should be integrated into the risk-assessment process. Appropriate interpretation of existing data from suitable guinea pig studies can provide valuable information with respect to potency, as the first step in the development of a risk assessment. However, for de novo investigations, the LLNA is the method favored for providing quantitative estimations of skin-sensitizing potency that are best suited to the risk assessment process. Finally, human testing is of value in the risk assessment process, but is performed only for the purposes of confirming product safety.

Evaluation of skin sensitization response of dialkyl (C6-C13) phthalate esters.

Isolated case reports suggest that dermal contact with some phthalate esters may result in skin sensitization. This issue was investigated in guinea pig sensitization tests, but the results were inconclusive. Consequently, 7 dialkyl phthalate esters, (diisohexyl, diisoheptyl, di(2-ethylhexyl), diisononyl, diisodecyl, diundecyl and ditridecyl phthalates), ranging in carbon number from C6 to C13, were tested in a 104-person panel human repeated insult patch test (HRIPT) using the modified Draize procedure. Test concentrations of 100% were selected for the induction and challenge phases of the HRIPT based upon a 24-h occluded irritation test on 15 panelists. Under the conditions of this HRIPT, no evidence of dermal irritation or sensitization for any of the 7 phthalate esters was observed in the 104-person panel. These HRIPT data provide evidence for the lack of experimental skin sensitization potential for the phthalate esters tested.

Skin sensitization risk assessment: a comparative evaluation of 3 isothiazolinone biocides.

Many of the chemicals in common use possess, to some degree, a capacity to cause skin sensitization. Consequently, it is important to conduct a thorough and accurate risk assessment when it can be anticipated that such chemicals are likely to come into contact with human skin. Such risk assessments must consider the nature and extent of dermal exposure together with the sensitizing potency of the chemical. Whilst the exposure elements of the risk assessment process are often well understood, or can at least be reasonably predicted on the basis of the proposed usage of the chemical, the determination of skin sensitizing potency may be problematic. In this paper, we describe an approach to the determination of relative potency of 3 isothiazolinone biocides. Initially, the local lymph node assay (LLNA) provides an estimate of relative sensitizing potency. Where appropriate, this can be followed by confirmatory testing in the human repeat insult patch test (HRIPT). The data generated reveal that (chloro)methyl isothiazolinone (CMI) is a significantly stronger sensitizer than either methyl trimethylene isothiazolinone (MTI) or benzisothiazolinone (BIT). Furthermore, both the LLNA and the HRIPT data show consistently that BIT is a somewhat weaker skin sensitizer than MTI. As an important additional component of the safety evaluation, the ability of these sensitizing isothiazolinones to cross-react has been considered; the data indicate that the more weakly sensitizing isothiazolinones do not elicit allergic reactions in subjects sensitized to MCI. The implications for use of these biocides in various product types are discussed.

Comparison testing of the irritancy of children's liquid bubble bath using a modified human repeat insult patch test

Background : Bubble baths are common products used by parents with young children. Some dermatologists and pediatricians do not recommend the use of these products. Objective : The purpose of this study was to compare the irritancy of nine children's liquid bubble bath solutions. Methods : A modified human repeat insult patch test (HRIPT) was used to rank order the irritancy of nine bubble bath preparations. Erythema, scaling, and fissuring were evaluated at the patch test sites. Results : The nine products tested varied in their ability to cause irritation. Based on the degree of erythema, the least irritation was produced with Sesame Street Fresh Apple Splash bubble bath. Conclusion : This study suggests that there are differences in the irritancy of brands of children's liquid bubble bath and that recommendations can be made by both dermatologists and pediatricians when parents choose to use these products on their children. This is a US government work. There are no restrictions on its use.

Comparison Testing of the Irritancy of Childrenʼs Liquid Bubble Bath Using A Modified Human Repeat Insult Patch Test

Background: Bubble baths are common products used by parents with young children. Some dermatologists and pediatricians do not recommend the use of these products. Objective: The purpose of this study was to compare the irritancy of nine children's liquid bubble bath solutions. Methods: A modified human repeat insult patch test (HRIPT) was used to rank order the irritancy of nine bubble bath preparations. Erythema, scaling, and fissuring were evaluated at the patch test sites. Results: The nine products tested varied in their ability to cause irritation. Based on the degree of erythema, the least irritation was produced with Sesame Street Fresh Apple Splash bubble bath. Conclusion: This study suggests that there are differences in the irritancy of brands of children's liquid bubble bath and that recommendations can be made by both dermatologists and pediatricians when parents choose to use these products on their children. This is a US government work. There are no restrictions on its use.

Comparison Testing of the Irritancy of Childrenʼs Liquid Bubble Bath Using A Modified Human Repeat Insult Patch Test

Comparison Testing of the Irritancy of Childrenʼs Liquid Bubble Bath Using A Modified Human Repeat Insult Patch Test

Skin Sensitization Potential of Polyethylene Glycols Evaluated in the Guinea Pig Maximization Test and the Human Repeat Insult Patch Test

The skin sensitization potential of five polyethylene glycols, ranging in average molecular weight from 200 to 8000, was evaluated by a guinea pig maximization test using the method of Magnusson and Kligman and a human repeat insult patch test. There was no evidence of sensitization to polyethylene glycols under the conditions of these two test systems.

Comparison testing of the irritancy of children's liquid bubble bath using a modified human repeat insult patch test

Comparison testing of the irritancy of children's liquid bubble bath using a modified human repeat insult patch test

Human Skin Irritation Studies of a Lecithin Microemulsion Gel and of Lecithin Liposomes

Soybean lecithin microemulsion gels offer promising features for the possible use as matrices in transdermal therapeutic systems. In order to assess the skin irritancy potential of the gel, acute and cumulative irriation tests were performed in human subjects in vivo using as comparison an unilamellar soybean lecithin liposome preparation and the solvent isopropyl palmitate (IPP). Acute irritation was tested in 151 volunteers in a 48-hour patch test, whereas cumulative irritation was assessed in a 21-day human repeated insult patch test in 20 volunteers. In the acute irritation test, discrete irritation (erythema only) developed with the gel in 2 subjects (1.3%), with the liposomes in 3 subjects (2.0%), and with IPP in 2 subjects (1.3%). For the assessment of cumulative irritation, the IT50 (irritation time of 50% of the test population) was calculated. IT50 was 13 days for the gel, 14 days for the liposomes and 17 days for IPP. This study shows a very low acute and a low cumulative irritancy potential for the soybean lecithin microemulsion gel making it a candidate matrix for transdermal therapeutic systems also under toxicological aspects.

Evaluation of the Skin Sensitization Potential of White Mineral Oil, Petrolatum, and Gelled White Oil

The skin sensitization potential of a white mineral oil and petrolatum was evaluated using a guinea pig sensitization assay; a gelled white oil was evaluated in a human repeated insult patch test. The use of mineral oils and petrolatums in applications involving repeated skin exposures provided the incentive to evaluate the sensitization potential of these substances. Neither the white mineral oil nor petrolatum produced a sensitization reaction in guinea pigs as judged by the reactions produced after challenge at a virgin site by a nonirritat-ing dose. The white oil gel did not produce skin sensitization in humans. These results support the use of these products in applications involving prolonged and repeated skin contact.

Human repeated insult patch test of 2‐butoxyethanol

Human repeated insult patch test of 2‐butoxyethanol

Final Report on the Safety Assessment of Lauramine and Stearamine

Lauramine and Stearamine are aliphatic amines intended for use in cosmetic formulations as antistatic agents, but no current uses have been reported. In a subchronic feeding study in rats, 3,000 ppm of Stearamine in the diet caused weight loss and increased mortality, with an accumulation of histiocytes in the mucosa of the small intestine and mesenteric lymph nodes. A diet of 500 ppm did not produce these effects. Dogs fed Stearamine at 15 mg/kg/day snowed the same histiocyte accumulation. In a 2-year chronic feeding study in rats, Stearamine at concentrations up to 500 ppm (maximum tested) showed no significant increase in the incidence of tumors. Stearamine at 0.01% in a high-fat diet promoted the carcinogenic effects of DMBA in female rats, whereas 0.1% significantly inhibited the production of tumors. Tests in animals showed Lauramine to cause severe dermal irritation and necrosis. Stearamine (in an ether vehicle) applied to the skin of albino mice caused severe hyperplasia at concentrations as low as 3 mg in a 0.2-ml application. These available data were insufficient to support the safety of Lauramine and Stearamine in cosmetic formulations. Additional data considered necessary to evaluate the safety of these ingredients include the following: impurities (especially data on nitrosamines); two different genotoxicity assays (one using a mammalian system and, if positive, a dermal carcinogenesis assay by National Toxicology Program standards may be required); and a human repeat-insult patch test. It cannot be concluded that these ingredients are safe for use in cosmetic products until the listed safety data have been obtained and evaluated.

An Approach to Allergic Contact Sensitization Risk Assessment of New Chemicals and Product Ingredients

Before introducing a new chemical or product into the market, we use a multistep process to assess contact sensitization risk for the product and key ingredients. The risk assessment process is a comparative toxicological approach in which data on the inherent toxicity of a material and the exposure to it (through manufacturing or consumer use or foreseeable misuse) are integrated and compared with data generated on benchmark materials of similar chemistry or product application, or both. The steps included in the risk assessment process include: (1) analytical characterization and literature review for skin sensitization data, (2) preclinical skin sensitization testing (murine local lymph node assay and/or Buehler guinea pig test), (3) human repeat insult patch testing (HRIPT), (4) clinical use testing, and (5) monitoring and follow-up of consumer comments. Our decision-tree approach to skin sensitization risk assessment is a dynamic process that incorporates numerous risk assessment points. The results obtained with the new material are compared with prior results with benchmark materials and then further evaluated relative to the type of exposure expected in the workplace and under normal use (and product misuse) conditions. This review summarizes each step of the contact sensitization risk assessment process and provides some specific examples to illustrate the value of the approach.