Cumulative irritancy test

Kligman and Wooding (1967) applied the Litchfield and Wilcoxon probit analysis to cumulative irritation testing with calculation of IT 50 and ID 50 values. Their early work forms the basis for the 21-day cumulative irritation assay, which is currently widely used. 

The reader should also be aware that there are a variety of cumulative irritancy test designs available, such as the guinea pig immersion test and the 21-consecutive-day occluded patch test in rabbits. 

Cumulative irritation test. This is another test that is commonly used to evaluate the absence of skin reactions to the formulation. It involves a minimum of 25 panelists. The solutions of test products as well as reference products with well-known skin tolerance are applied to the backs of panelists under occlusion for several consecutive days (generally 5 or 21 days) and the absence of skin reaction is then evaluated by trained professionals [22],... 

Other animal tests have been used to study skin irritation by surfactants or other chemicals and have been reviewed by Gabriel [50]. They are the mouse ear swelling test, the guinea pig immersion technique, the cumulative irritation test on rabbits, and the rabbit ear test. As their usage is continually declining, the reader is referred to Ref. 50 for further details. 

A 14-day cumulative irritation test was mn [40]. The number of days it takes a product to produce irritation (score of 1) were determined. The longer it takes a product to reach a score of 1, the milder the product. Table 5 shows a comparison of various surfactants to sodium lauryl sulfate, an irritating control. As can be seen, the SME and sulfonated fatty-acid samples evaluated were as mild as the 3-mole ether sulfate and isethionate tested. These surfactants are recognized in the industry as mild. 

TABLE 5 Comparative Irritation Study via 14-Day Cumulative Irritation Test... 

In a third report (very similar to the second), Hanhijarvi, Nevalainen and Mannisto (1985) clearly demonstrated that the type of vehicle can greatly influence irritation, in that dithranol was clearly more irritating when applied in paraffin that when applied in a gel. They were also able to demonstrate that although dithranol was less acutely irritating than butantrone, the cumulative irritations (mean scores at the end of six months of six times per week applications) were quite similar (Mannisto et al., 1984). There was no evidence of systemic toxicity nor of test article in plasma with either species. 

These are conducted to gain information on the cumulative irritancy of a product. This type of test is designed to mirror the intended use of the product, but exposure may also be exaggerated, to provide a greater margin of safety in the risk assessment on the product and also to provide information on problems that may be encountered should the product be misused. Some methods are designed to simulate the normal use of products, with controlled exposure. The skin irritation is monitored and comparisons made between the test and control product in the same panellist. The controls are... 

These are animal assays that evaluate the ability of chemicals to produce cumulative irritation. Many such tests have been described in literature, but only a few have been studied extensively enough to mention. Even those used more often are not as well standardized as Draize-type tests, and many variables have been introduced by multiple investigators. 

PURPOSE AND RATIONALE Inflammation produced late in the induction phase of sensitization tests without positive responses at challenge is cumulative irritation. The HRIPT for skin allergy was modified to evaluate skin irritation. As with single-application patch tests, many investigators developed their own version of the repeat application patch test. 

Safety testing for cosmetics includes usually cumulative irritation, RIPT, phototoxicity, photoallergy, and finally, exaggerated use or home use studies. 

Cumulative irritation The scope of this study is to determine long-term irritation potentials under exaggerated conditions or to assess and compare the mildness of formulations. It consists of a controlled patch test involving 15-30 subjects using 14-21 repetitive 24 h applications. The FDA recommends a 21 day patch test in a 30-subject panel. For more irritating cosmetics, a 14 day application would satisfy the objective of the study. 

It is unlikely that there will be significant percutaneous toxicity under the usual conditions of exposure to screening smokes. However, if primary and cumulative skin irritation tests suggest that there may be systemic effects, then it will be appropriate to conduct more detailed monitored studies for percutaneous toxicity. 

Individual daily observations should be provided, as well as a tabulation that presents the percentage of subjects with each grade of skin reaction and degree of patch adherence on each study day. The mean cumulative irritation score, the total cumulative irritation score, and the number of days until sufficient irritation occurred to preclude patch application for all the study subjects should be calculated for each test product, and a statistical analysis of the comparative results should be performed (see Appendix C). 

Skin irritation can be produced by nonimmune-mediated idiosyncratic cutaneous reactions resulting from cumulative toxicity, overdose, drug interactions, and metabolic alterations (Lee and Thompson, 2006). RhE skin irritation tests (SIT) have been validated and adopted by OECD as TG 439 for determining the irritation hazard from topical exposure to chemicals and mixtures (Kandarova et al., 2009 OECD, 2009). TG 439 is based on the ability of irritant chemicals to penetrate the stratum comeum and produce cytotoxicity in the underlying cell layers. The TG classifies test substances as either irritating or nonirritating based on results of the MTT viability assay. 

Some chemicals do not produce acute irritation from a single exposure, but may produce inflammation following repeated application to the same area of skin (cumulative irritation) (Shelanski 1951). Studies of skin corrosion are conducted in animals using standardized protocols, as it is not appropriate to conduct screening studies in humans. However, acute irritation is sometimes evaluated in humans after animals studies have been completed. Tests for cumulative irritation in both animals and humans have been reported. 

The cumulative irritation assay as described by Lanman and coworkers (1968) was used to compare antiperspirants, deodorants, and bath oils to provide guidance for product development. A 1 inch of Webril was saturated with test compound and applied to the skin of the upper back. After 24 h, the patch was removed, the area evaluated, and a fresh patch applied. The procedure was repeated daily for up to 21 days. The time it took to produce an irritant response in 50% of the test subjects [IT50, as... 

Many bioassays have been proposed for the purpose of identifying sensitive skin. A 24-h patch test with sodium lauryl sulphate (SLS) and repetitive patch tests, such as the 21-day cumulative-irritation assay, the chamber scarification test, and the soap-chamber test, have been used (Lee and Maibach 1994). 

Whilst the test described above is a common way in which an attempt is made at predictive identification of those substances or products with significant skin-irritation potential, other information can also be used. Consideration is given to structure-activity relationships, although it must be said that this subject is in its infancy for skin irritants (Whittle et al. 1996 Barratt 1996). Data may also come from non-standard animal tests, predictive human tests and from human experience. These may cover either acute and/or cumulative irritant responses in skin. It is also possible for manufacturers to use data from in vitro studies. Lastly, where the product is a mixture of two or more substances [a preparation in European Union (EU) terminology], the manufacturer may elect to calculate the likely irritancy on the basis of the knowledge of the skin irritancy of the component substances and the concentration at which they occur in the product. For certain types of product, this process has been formalised in the EU as the conventional method (European Community 1988). 

Alcohols can delipidize and dehydrate the upper part of the stratum corneum, thereby impairing the barrier function of the epidermis. Irritant contact dermatitis from alcohol is most often of the cumulative irritant contact type and, in rare cases, of the acute irritant type (Adams 1986 Tupker et al. 1997). Alcohol dermatitis may take the form of an eczematous eruption, or, more rarely, a contact urticarial at the exposed site (Martin Scott i960 Fregert et al. 1963). Allergic contact dermatitis to ethanol and isopropanol is considered rare (Pecquet and Pradalier 1992), but was reported as a constituent of a transdermal patchsystem (Okazawa et al. 1998). The patch test concentrations for these substances are either as is or in 10% aqua. 

This cumulative application test has the advantage over the previous ones because it is able to detect even weak irritants so that false negatives are extremely rare and a product causing minimal irritation in this test is very unlikely to cause skin irritation when placed on the market. 

Organophosphate Ester Hydraulic Fluids. Repeated application of a patch treated with 0.2 pL of Skydrol 500B-4 for 5 weeks (3 times/week) resulted in mild cumulative erythema confined to the contact site in 14 of 53 human test subjects, beginning with the third dose during the first week. No evidence of immediate primary dermal irritation was observed (Monsanto 1980). 

Epichlorohydrin can cause central nervous depression and irritation of the respiratory tract death is generally due to depression of the respiratoiy centre (Hine Rowe, 1963). Nephrotoxicity is a cumulative effect of epichlorohydrin poisoning (Hine Rowe, 1963 Pallade et al., 1968) renal insufficiency occurred within 24-48 h in approximately 80% of rats that had been given 125 mg/kg bw of the compound (Pallade et al., 1968). Epichlorohydrin produces extreme irritation when tested intradermally, dennally or intra-ocularly in rabbits (Lawrence et al., It caused skin sensitization in 60% (9/15) of... 

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