The open epicutaneous test (OET) (28) simulates the conditions of human use by utilizing topical application of the test material. The procedure determines the doses required to induce sensitization and to elicit a response in sensitized animals. The irritancy profile is determined by applying 0.025 mL of varying concentrations to a 2 cm2 area of the shaved flanks of six to eight guinea pigs. Test sites are visually evaluated 24 h after application of test solutions to erythema. The dose not causing a reaction in any animal (maximal nonirritant concentration) and the dose causing a reaction in 25% of the animals (minimal irritant concentration) are determined. During induction, test solution is applied to flank skin of six to eight guinea pigs for 3 weeks, or 5 times a week for 4 weeks. A control group is treated with vehicle only. The highest dose tested is usually the minimal irritant concentration and lower doses are based on usage concentration or a step-wise reduction. Twenty-four to 72 h after the last induction treatment, each animal is challenged on the untreated flank. The minimal irritant concentration, the maximum nonirritant concentration and five solutions of lower concentrations are applied. Skin reactions are read on an all-or-none basis at 24, 48, and 72 h after application. The maximum nonirritating concentration in the vehicle-treated group is calculated. Animals in test groups that develop inflammatory responses to lower concentrations are considered sensitized.
BUEHLER TEST £
The Buehler test (occlusion only) (29) also employs topical application. An absor- <
bent patch, or vehicle alone, is placed on the shaved flanks of 10 to 20 guinea pigs. Test concentration varies from undiluted to usage levels. A concentration
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Rosacea and Eczema are two skin conditions that are fairly commonly found throughout the world. Each of them is characterized by different features, and can be both discomfiting as well as result in undesirable appearance features. In a nutshell, theyre problems that many would want to deal with.