Human and Rabbit Eye Responses to Chemical Insult

Human and Rabbit Eye Responses to Chemical Insult. FREEBERG,F.E., NIXON, G.A., REER, P.J., WEAVER, J.E., BRUCE, R.D., GRIFFITH,J.F., AND SANDERS, L.W., Ill (1986). Fundam Appl. Toxicol. 7,626-634. Groups of eight human volunteers and eight albino rabbits,under controlled laboratory conditions, were exposed in oneeye without subsequent rinsing to the same concentrations andvolumes of four prototype consumer products: fabric softener,shampoo, hand soap, and laundry detergent. Dose volume was 0.10or 0.01 ml. The dose concentrations were selected to producemoderate effects with recovery within 24 to 48 hr. Two irritationscales were employed with both human and animal subjects: theDraize scale by a technician and a medical scale used with slitlamp examination by an ophthalmologist. Eyes were examined byboth graders before and after dosing at specified intervalsuntil recovery. Mean and maximum irritation scores are presentedfor each grading time, method, and exposure, as are the meanhours to recovery (clearing) for each exposure. Recovery timesfor human eyes were consistent with those reported previouslyfor accidental human exposures to similar materials. Correlationcoefficients for time to clear, comparing human vs rabbit foreach dose volume-species combination across the four test products,were 0.72, 0.1 ml-human vs 0.01 ml-rabbit; 0.66, 0.01 ml-humanvs 0.01 ml-rabbit; 0.40, 0.01 ml-human vs 0.1 ml-rabbit; 0.35,0.1ml-human vs 0.1 ml-rabbit. Thus, recovery time obtained underconditions of the "Low-Volume" test (0.01 ml-rabbit) bettercorrelates with human eye recovery time (either dose volume)than does recovery time under Draize test conditions (0.10 ml-rabbit).It is concluded that a rabbit eye test based on a 0.01-ml dosevolume (low volume test) more accurately predicts human occularresponse than does the Draize test and should be used to judgenew eye irritation methods.     

In vitro eye irritancy test of lauryl derivatives using the reconstructed rabbit corneal epithelium model

The rabbit corneal epithelium model (RCE model) was developed as a three-dimensional in vitro model to replace animal testing for the assessment of eye tolerance. In the model, a stratified culture of rabbit corneal epithelial cells is grown at the air–liquid interface on an amniotic membrane acting as a parabasal membrane. The alkaline exposure was restored each day in the presence of no irritants, although with the addition of SLS, which is a major irritant, the restoration of deficit was inhibited on the RCE model in a dose-dependent manner. The results of this test were comparable with those of the Draize test, and thus, this method using the RCE model may prove to be a useful and sensitive in vitro eye irritation test. The lauryl fatty chain derivatives, such as polyoxyethylene (9) lauryl ether (PLE), sodium polyoxyethylene (2) lauryl ether sulfate (SPLE), mono glyceryl laurate (MGL), and sodium N-lauroyl-l-glutaminate (SLG), which are widely used as surfactants for toiletry products and cosmetics, were evaluated for in vitro eye irritation potential using the RCE model. SLS, PLE, SPLE, MGL, and SLG inhibited 88.7%, 59.2%, 69.0%, 47.5%, and 15.7% of the restoration of deletion 24 h after treatment at a concentration of 0.05%. The IC₅₀ (50% inhibitory concentration) values of SLS, PLE, SPLE, MGL, and SLG were 0.002%, 0.021%, 0.005%, 0.056%, and 0.448%, respectively. These results indicated that a functional group at the end of lauryl chain is an important factor for inhibiting the restoration of deletion using the RCE model.     

Subchronic (26- and 52-week) toxicity and irritation studies of a novel microbicidal gel formulation containing sodium lauryl sulfate in animal models

The safety of an ethylene oxide/propylene oxide gel formulation containing sodium lauryl sulfate (2%, w/w), that could be a potent candidate as a topical microbicide, has been evaluated. More specifically, the subchronic (26- and 52-week) toxicity of the formulation when applied intravaginally as well as its irritating potential for the rectal, penile, eye, skin and buccal mucosa have been examined in animal models. The results showed that the vaginal administration of the gel formulation containing sodium lauryl sulfate once and twice daily (with doses 12 +/- 2 h apart) for 26 weeks to rats and for 52 weeks to rabbits induced slight to moderate histopathological alterations. When the formulation was applied intrarectally to male and female rabbits once and twice daily (with doses 12 +/- 2 h apart) for 14 days, no macroscopic or microscopic changes were reported. For both vaginal and rectal dosing, no effect was seen on the haematology, coagulation and serum chemistry parameters as well as on the body weight of animals and the relative organ weights. Other sporadic macroscopic and histopathological findings were incidental in origin and of no toxicological significance. The gel formulation containing sodium lauryl sulfate was considered as mildly irritating for the penile mucosa of rabbits, non-irritating for the eye of rabbits, mildly irritating for the skin in a rabbit model and non-irritating for the hamster cheek pouch. It is suggested that the gel formulation containing sodium lauryl sulfate is safe for most tissues that could be exposed to the product under normal use.     

A tiered approach to the use of alternatives to animal testing for the safety assessment of cosmetics: Skin irritation

Evaluation of the skin irritancy and corrosivity potential of an ingredient is a necessity in the safety assessment of cosmetic ingredients. To date, there are two formally validated alternatives to the rabbit Draize test for skin corrosivity in place, namely the rat skin transcutaneous electrical resistance (TER) assay and the Human Skin Model Test using EpiSkin™, EpiDerm™ and SkinEthic™ reconstructed human epidermal equivalents. For skin irritation, EpiSkin™, EpiDerm™ and SkinEthic™ are validated as stand-alone test replacements for the rabbit Draize test. Data from these tests are rarely considered in isolation and are evaluated in combination with other factors to establish the overall irritating or corrosive potential of an ingredient. In light of the deadlines established in the Cosmetics Directive for cessation of animal testing for cosmetic ingredients, a COLIPA scientific meeting was held in Brussels on 30th January, 2008 to review the use of alternative approaches and to set up a decision tree approach for their integration into tiered testing strategies for hazard and safety assessment of cosmetic ingredients and their use in products. In conclusion, the safety assessments for skin irritation/corrosion of new chemicals for use in cosmetics can be confidently accomplished using exclusively alternative methods.     

Histopathology in the isolated chicken eye test and comparison of different stainings of the cornea

The isolated chicken eye (ICE) test, developed at our Institute, is accepted by the OECD for identification of severe eye irritants. The OECD ICE Guideline (No. 438) encourages preservation of the treated eyes for possible histopathology of the cornea, which is believed to strengthen evidence of absence or presence of irritation and to help clarify borderline effects by assessment of the corneal Depth-of-Injury. Histopathology of the cornea in addition to the normal slit-lamp microscope assessment of corneal effects has already been performed routinely in ICE tests at our Institute, using two standard stainings (H&E and PAS). In this study, three other stainings (AZAN, EVG and Trichrome), more specific for collagen-rich membranes such as basement- and Bowman’s membranes were examined with corneas exposed to four model compounds ranging from non- to severely irritating (corrosive). PAS appeared to be the superior staining method. Surprisingly, the well-known eye corrosive sodium hydroxide (NaOH, solid) did not visibly compromise the integrity of Bowman’s or the basement membrane. Based on our experience, histopathology of the treated cornea is confirmative in relation to the standard assessment of eye irritation by slit-lamp observation in the ICE and in certain cases can help to evaluate borderline effects. Besides establishing the depth of injury, additional investigation of corneal limbal stem cell damage after chemical exposure might be appropriate to determine reversibility or irreversibility of eye effects.     

Prediction of eye irritation from organic chemicals using membrane-interaction QSAR analysis.

Eye irritation potency of a compound or mixture has traditionally been evaluated using the Draize rabbit-eye test (Draize et al., 1944). In order to aid predictions of eye irritation and to explore possible corresponding mechanisms of eye irritation, a methodology termed "membrane-interaction QSAR analysis" (MI-QSAR) has been developed (Kulkarni and Hopfinger 1999). A set of Draize eye-irritation data established by the European Center for Ecotoxicology and Toxicology of Chemicals (ECETOC) (Bagley et al., 1992) was used as a structurally diverse training set in an MI-QSAR analysis. Significant QSAR models were constructed based primarily upon aqueous solvation-free energy of the solute and the strength of solute binding to a model phospholipid (DMPC) monolayer. The results demonstrate that inclusion of parameters to model membrane interactions of potentially irritating chemicals provides significantly better predictions of eye irritation for structurally diverse compounds than does modeling based solely on physiochemical properties of chemicals. The specific MI-QSAR models reported here are, in fact, close to the upper limit in both significance and robustness that can be expected for the variability inherent to the eye-irritation scores of the ECETOC training set. The MI-QSAR models can be used with high reliability to classify compounds of low- and high-predicted eye irritation scores. Thus, the models offer the opportunity to reduce animal testing for compounds predicted to fall into these two extreme eye-irritation score sets. The MI-QSAR paradigm may also be applicable to other toxicological endpoints, such as skin irritation, where interactions with cellular membranes are likely.     

凝胶色谱法测定注射用头孢唑肟钠中聚合物的含量

目的：建立Sephadex G-10凝胶色谱系统分析头孢唑肟钠高分子聚合物的方法。方法：色谱柱为葡聚糖凝胶G-10柱（16 mm×650 mm）,流动相A为0.01 mol/L磷酸盐缓冲液（pH7.0）,流动相B为0.01%十二烷基硫酸钠溶液,流速：2.5 ml/min,检测波长：254 nm,进样量：200μl。结果：头孢唑肟钠进样浓度在5~200 mg/ml的范围内与头孢唑肟钠高分子聚合物的峰面积呈良好的线性关系（r=0.999 2）。结论：该方法简便准确、灵敏度高、重现性好。     

An objective procedure for quantitating eye irritation based upon changes of corneal thickness

For four decades, the Draize test has remained the accepted method for evaluating eye irritation. Criticisms center around the inhumane treatment of animals and the irreproducibility of the subjective scoring procedure. The objective of this study was to determine if changes in corneal thickness obtained using a slit-lamp pachometer could be used to replace the Draize scoring procedure and provide a method for quantifying ocular irritation. Twenty-four chemicals (six surfactants, seven alcohols, four ketones, four acetates, and three aromatics) were instilled in the conjunctival sacs of rabbits and irritation monitored by Draize scoring and changes in corneal thickness. The Draize procedure was more adept at detecting minor conjunctival damage, but corneal thickness exhibited less variation and increased sensitivity for detection of healing reactions. A significant linear correlation (y = 1.736x + 92.883) was established between Draize score and corneal thickness changes with a correlation coefficient (r) of 0.86 and an F-value for regression of 261.3. Using these findings, an ocular irritation ranking system is proposed based upon the percentage of corneal swelling. Ocular irritation potential was ranked for the chemical groups tested (surfactants > alcohols > ketones or acetates > aromatics). Quantitation of ocular irritation from changes in corneal thickness provides objective, numerical data applicable to standard parametric statistical procedures. This should eliminate the subjective bias inherent to Draize scoring and decrease intra- and interlaboratory variability.     

Alternative methods for eye and skin irritation tests: an overview

The evaluation of eye and skin irritation potential is essential to ensuring the safety of individuals in contact with a wide variety of substances designed for industrial, pharmaceutical or cosmetic use. The Draize rabbit eye and skin irritancy tests have been used for 60 years to attempt to predict the human ocular and dermal irritation of such products. The Draize test has been the standard for ocular and dermal safety assessments for decades. However, several aspects of the test have been criticised. These include: the subjectivity of the method; the overestimation of human responses; and the method's cruelty. The inadequacies of the Draize test have led to several laboratories over the last 20 years making efforts to develop in vitro assays to replace it. Protocols that use different types of cell cultures and other methods have been devised to study eye and skin irritation. Different commercial kits have also been developed to study eye and skin irritation, based on the action of chemicals on these tissues. This article presents a review of the main alternatives developed to replace the use of animals in the study of chemical irritation. Particular attention is paid to the reproducibility of each method.     

Draize rabbit eye test compatibility with eye irritation thresholds in humans: a quantitative structure-activity relationship analysis.

Draize rabbit eye test scores, as modified maximum average score (MMAS), for 68 pure bulk liquids were adjusted by the liquid-saturated vapor pressure P. These 68 adjusted scores, as log (MMAS/P), were shown to be completely equivalent to eye irritation thresholds (EIT), expressed as log (1/EIT), for 23 compounds in humans. Thus, for the first time the Draize eye test in rabbits for pure bulk liquids is shown to be perfectly compatible with eye irritation thresholds in humans. The total data set for 91 compounds was analyzed by the general solvation equation of Abraham. Values of log (MMAS/P) or log (1/EIT) could be fitted to a five-parameter equation with R2 = 0.936, SD = 0.433, AD = 0.000, and AAD = 0.340 over a range of 9.6 log units. When divided into a training set of 45 compounds, the corresponding equation could be used to predict the remaining 46 compounds in a test set with AD = -0.037 and AAD = 0.345 log units. Thus, the 91-compound equation can now be used to predict further EIT values to around 0.4 log units. It is suggested that the mechanism of action in the Draize test and in the human EIT involves passive transfer of the compound to a biophase that is quite polar, is a strong hydrogen bond base, a moderate hydrogen bond acid, and quite hydrophobic. The biophase does not resemble water or plasma, but resembles an organic solvent such as N-methylformamide.     

Interlaboratory assessment of alternatives to the Draize eye irritation test in Germany

A national interlaboratory study to validate two alternative methods to the Draize rabbit's eye test, co-ordinated by ZEBET at the German Federal Health Office (BGA), is described. The aim of the study is to classify chemicals according to their irritation potential using the neutral red/kenacid blue (NR/KB) cytotoxicity assay and the hen's egg chorioallantoic membrane (HET-CAM) test. During the last two years 12 toxicology laboratories from industry, universities and other research institutions have tested 32 substances from a variety of chemical classes, characterized by a broad spectrum of locally irritating properties, using the NR/KB cytotoxicity test and the HET-CAM assay. Intra- and interlaboratory reproducibility of the two methods was investigated under standardized conditions. The so-far limited evaluation of the interlaboratory assessment phase of validation indicates that the results of the Draize rabbit's eye test correlate better with the results of the HET-CAM test than with those of the cytotoxicity test as far as false negative results are concerned. However, the intra- and interlaboratory reproducibility of the cytoxicity test is better than that of the HET-CAM test. The validation project has recently entered the stage of database development during which 150 chemicals will be tested in seven laboratories to provide information on whether and to what extent the NR/KB test and the HET-CAM test can replace the Draize rabbit's eye test for the classification and labelling of chemicals with regard to their eye irritation potential.     

Development of the short time exposure (STE) test: an in vitro eye irritation test using SIRC cells.

Using SIRC (rabbit corneal cell line) cells, we developed an alternative eye irritation test: the short time exposure (STE) test. This STE test is a cytotoxicity test using physiological saline or mineral oil as the test solvent. Evaluation exposure time is short (5 min), which is similar to actual exposure situations, and uses the cell viability (CV) at a constant concentration as the endpoint for irritation potential. First, in order to confirm the usefulness of this STE test in assessing eye irritation potential of chemicals, 51 raw materials were tested and the correlation between CV in the STE test and the eye irritation score in the Draize test was examined. For the undiluted raw materials tested in the Draize test, the 5% test concentration in the STE test gave irritation classes that correlated well with the irritation classes from the Draize test (accuracy: 89.6%). For those materials tested as a 10% solution in the Draize test, STE irritation classes with 0.05% test concentration corresponded well with the Draize irritation classes (accuracy: 80.0%). Next, using the cell viabilities at these two concentrations, the STE prediction model (PM) was developed. A score of 1 or 2 was given for the results from each tested concentration in the STE test and Draize test. The scores from each test were then summed to yield a 3-level (Rank 1: minimally irritant, Rank 2: moderate irritant, Rank 3: severe irritant) eye irritation potential classification. Rank classification in the STE test showed a good correlation mostly to that in the Draize test (irritation class correspondence rate: 70.2%, but after exclusion of data of alcoholic materials, the rate was 91.7%). In most cytotoxicity test, the cytotoxicity of acids and amines is generally underestimated due the use of medium as the solvent. This is the result of the buffering capacity of the media. On the other hand, the STE test could predict the eye irritation potential by evaluating the chemical with a 5% test concentration. Eleven water insoluble materials such as toluene, octanol, and hexanol could be evaluated by using mineral oil as test solvent in the STE test. The STE test demonstrated itself to be simple, promising, have great potential, be of value, and to be an easily standardized alternative eye irritation test.     

Assessment of skin absorption and irritation potential of arachidonic acid and glyceryl arachidonate using in vitro diffusion cell techniques.

Arachidonic acid (AA), a precursor of pro-inflammatory mediators, and its glycerin ester, glyceryl arachidonate (GA), are reportedly used in cosmetic products. In vitro skin penetration of AA and GA and GA's ester hydrolysis was determined in flow-through diffusion cells. AA penetration with human and rat skin was 19.5% and 52.3% of the applied dose respectively, a substantial amount of which remained in the skin at 24h. Similar penetration results were obtained with GA in human skin. However, GA penetration through cultured skin (EpiDerm) was 51% of the applied dose, almost all of which appeared in the receptor fluid. At least 27.8% of GA penetrating skin was hydrolyzed to AA. In vitro methods were used to assess skin irritation in diffusion cells. Skin irritation of AA, sodium lauryl sulfate (SLS), and Tween 80 was determined by changes in transepidermal water loss (TEWL), skin viability (3-(4,5-dimethylthiaxol-2-yl)-2,5-diphenyltetrazolium bromide, MTT, formation), and cytokine release (IL-1alpha). SLS irritation was much less pronounced in an emulsion versus an aqueous vehicle. No significant irritation was observed in vitro from AA in an emulsion. This work predicts that AA would penetrate human skin in vivo and that it could be formed in skin from topically applied GA.     

Studies on eye irritation caused by chemicals in rabbits--II. An in vitro testing method using rat red blood cells for the prediction of eye irritation potential of chemicals

Rat red blood cells were used as an in vitro method to evaluate the eye irritation potential of chemicals in rabbits. The results using 116 chemicals of various categories including medicines, pesticides, detergents and solvents were analyzed for the prediction of possibility of eye irritation potentials. Eye irritation of chemicals was examined according to Draize method and chemicals were classified into three categories, (1) non or mild irritants, (2) moderate or severe irritants and (3) strong or corrosive irritants, based on the recovery of damages. The in vitro method consisted of two methods detecting the effects of chemicals mainly on protein and lipid in the membrane, which were evaluated by the induction of methemoglobin and hemolysis, respectively. Non- or mild irritants induced neither methemoglobin formation nor hemolysis. Most of moderate or severe irritants induced hemolysis, however, the potentials were low. Strong or corrosive irritants had high potentials for the induction of methemoglobin. The multivariate estimation by the above two in vitro data sets were 77.6% predictive of the in vivo classification.     

The Short Time Exposure (STE) test for predicting eye irritation potential: Intra-laboratory reproducibility and correspondence to globally harmonized system (GHS) and EU eye irritation classification for 109 chemicals

Short Time Exposure (STE) test is an easy in vitro eye irritation test that assesses cytotoxicity in SIRC cells (rabbit corneal cell line) following a 5 min dose treatment. To assess intra-laboratory reproducibility, medium control, three vehicles (saline, saline containing 5% (w/w) dimethyl sulfoxide, and mineral oil) and three standard chemicals (sodium lauryl sulfate, calcium thioglycolate, and Tween 80) were evaluated. Assessments were repeated 30 times for vehicles and 18 times for standard chemicals; resulting in almost the same cell viability and a low coefficient of variation value. In addition, the STE eye irritation rankings of three standard chemicals, as calculated on the cell viabilities in 5% and 0.05% solutions were in agreement in all tests. Based on these results, high intra-laboratory reproducibility was confirmed.In addition, the irritation category (irritant and non-irritant) was evaluated for 109 chemicals with STE test, globally harmonized system (GHS) classification, and European Union (EU) classification. The results of the evaluation found the STE classification to have an accuracy with GHS classification of 87% and with EU classification of 83%, which confirmed the excellent correspondence.The correspondence of STE rankings (1, 2, and 3) based on the prediction model by STE test with the eye irritation rankings by GHS (non-irritant, categories 2 and 1) and EU (non-irritant, R36, and R41) was 76% and 71%, respectively.Based on the above results, STE test was considered to be a promising alternative method for assessing eye irritation that has high intra-laboratory reproducibility as well as an excellent predictability of eye irritation.     

Characterization of new eye drops with choline salicylate and assessment of their irritancy by in vitro short time exposure tests

The aim of our study was to examine the irritation potential of new eye drops containing 2% choline salicylate (CS) as an active pharmaceutical ingredient (API) and various polymers increasing eye drop viscosity (hydroxyethylcellulose, hydroxypropyl methylcellulose, methylcellulose, polyvinyl alcohol, polyvinylpyrrolidone). The standard method for assessing the potential of irritating substances has been the Draize rabbit eye test. However the European Centre for Validation of Alternative Methods and the Coordinating Committee for Validation of Alternative Methods recommend, short time exposure (STE) in vitro tests as an alternative method for assessing eye irritation. The eye irritation potential was determined using cytotoxicity test methods for rabbit corneal cell line (SIRC) after 5 min exposure. The viability of cells was determined using two cytotoxicity assays: MTT and Neutral Red Uptake. According to the irritation rankings for the short time exposure test, all tested eye drops are classified as non-irritating (cell viability >70%).     

三维重组眼角膜上皮模型法与兔眼刺激法对洗发水眼刺激性的比较与评价

目的 本文同时采用三维人重组角膜模型BioOcular?和现行的兔眼刺激Daize法,对市面常见的不同配方洗发水的眼刺激性进行评价与比较。方法 参考体外眼刺激实验(OECD指导原则492),采用人重组眼角膜上皮模型和兔眼刺激法对8种不同品牌洗发水的眼刺激性进行评价研究。结果 研究表明,与传统兔眼实验比较,采用皮肤模型的眼刺激法对8种洗发水有无刺激性的区分结果与兔眼刺激法基本一致。其中两种方法相关系数r达到0.955,具有很好的相关性。结论 与兔眼刺激法相比,人重组眼角膜上皮模型刺激实验所需的周期短、试验步骤相对简便、检测结果相对更加客观,人源重组组织与人眼刺激更为接近,是一种值得推荐的眼刺激替代检测方法。     

Classification and labeling of industrial products with extreme pH by making use of in vitro methods for the assessment of skin and eye irritation and corrosion in a weight of evidence approach

Classification and labeling of products with extreme pH values (?2 or ?11.5) is addressed in chemicals legislation. Following determination of pH and alkaline/acid reserve, additional in vitro tests are needed, especially to substantiate results less than corrosive. However, only limited experience with the practical application of in vitro methods to determine appropriate classifications for pH extreme products is available so far. Expert judgment and weight of evidence are given major roles under the globally harmonized system of classification and labeling of chemicals (GHS) and should be performed on a sound data basis. We have used a tiered testing strategy to assess 20 industrial products (cleaning and metal pretreatment) regarding their corrosive and irritating properties towards human skin models in vitro in the EpiDerm™ skin corrosion and/or skin irritation test. Nine dilutions of individual compounds were additionally tested. Non-corrosive samples were tested in the Hen’s egg test chorioallantoic membrane (HET-CAM). We demonstrate how data is combined in a weight of evidence expert judgment, and give examples of classification decisions. To our knowledge this is the first comprehensive analysis of industrial products with extreme pH values to determine irritating and corrosive properties by making use of in vitro methods in a weight of evidence approach.     

Effects of Age on the Sensitivity of the Rat Lens to Hexanol in Vitro

Abstract

The Draize eye irritation test involves the injection of 0.1 ml of a test material into the conjunctival sac of young adult rabbits. A numerical scale is used to determine if the chemical is an irritating or nonirritating substance. This is the standard eye irritancy test used today. Aside from ethical concerns, and concerns related to the subjectivity of the measures, the Draize test fails to acknowledge whether there is a change in sensitivity of the eye to irritation as the subject ages. Some chemicals, particularly cosmetics and shampoos, are used throughout a human lifespan. A rat lens model of young (2.5-month) versus older (16-month) animals was used to show that there is a change in the sensitivity to a known irritant, hexanol, with age, and that recovery (repair of incurred damage) is also age dependent. The optics of the in vitro lens, tested using a specially developed Scanning Lens Monitor, are sensitive enough to show small variations in hexanol damage with various aged lenses. Lenses from 2.5- and 16-month-old rats showed 100% increases in focal length variability (optical focus), respectively, at 0.6 ± 0.7 and 10.0 ± 5.3 h after removal from a 2 h exposure to 100% hexanol. Recovery was seen only with the younger lenses at 46.8 ± 5.5 h.     

Comparative assessment of the acute skin irritation potential of detergent formulations using a novel human 4-h patch test method

Predictive skin irritation test methods, which do not require use of animals, are needed for the pre-market assessment of detergent formulations. The utility of a novel and ethical human acute skin irritation patch test method, originally developed for chemical skin irritation assessment, was evaluated. In this IRB-approved method, subjects were patched under occlusion for increasing periods of time up to 4 h in duration. The total incidence of positive skin reactions for test products was compared to a positive control (20% aqueous sodium dodecyl sulfate [SDS]). Acutely irritating formulas were defined as those showing a significantly increased or equal incidence of positive responders compared with that of SDS. The time of exposure required for 50% of subjects to show a positive skin reaction (TR₅₀ value) was calculated for each product and enabled test product comparisons within and between studies. Using this approach, 24 detergent formulations of various types were tested in seven individual studies. The skin irritation profiles were generally consistent within product types, which could be categorized as follows (by decreasing irritancy): mold/mildew removers (average TR₅₀ = 0.37 h) > disinfectants/sanitizers (0.64 h) > fabric softener concentrate (1.09 h) = aluminum wash (1.20 h) > 20% SDS (1.81 h) > liquid laundry detergents (3.48 h) > liquid dish detergents (4.16 h) = liquid fabric softeners (4.56 h) = liquid hand soaps (4.58 h) = shampoos (5.40 h) = hard surface cleaners (6.34 h) > powder automatic dish detergents (>16 h) = powder laundry detergents (>16 h). In addition to formulation effects, some seasonal effects were noted; particularly greater winter-time reactivity to 20% SDS and the hard surface cleaner and liquid laundry formulations. These results demonstrate the utility of this patch test method for the comparative skin irritation assessment of these different product types.