333-016-0025 Method of Testing Primary Irritant Substances (1) Primary irritation to the skin is measured by a patch test technique on the abraded and intact skin of the albino rabbit, clipped free of hair. A minimum of six subjects are used in abraded and intact skin tests. Introduce under a square patch such as surgical gauze measuring 1" X 1" two single layers thick, 0.5 milliliter (in the case of liquids) or 0.5 gram (in the case of solids and semi-solids) of the test substance. Dissolve solids in an appropriate solvent and apply the solution as for liquids. The animals are immobilized with patches secured in place by adhesive tape. The entire trunk of the animal is then wrapped with an impervious material such as rubberized cloth, for the 24-hour period of exposure. This material aids in maintaining the test patches in position and retards the evaporation of volatile substances. After 24 hours of exposure, the patches are removed and the resulting reactions are evaluated on the basis of the designated values in the following evaluation of skin reactions: (a) Erythema and eschar formation: (A) No erythema — Value of 0; (B) Very slight erythema (barely perceptible) — Value of 1; (C) Well-defined erythema — Value of 2; (D) Moderate to severe erythema — Value of 3; (E) Severe erythema (beet redness) to slight eschar (injuries in depth) — Value of 4. (b) Edema formation: (A) No edema — Value of 0; (B) Very slight edema (barely perceptible) — Value of 1; (C) Slight edema (edges of area well defined by definite raising) — Value of 2; (D) Moderate edema (raised approximately 1 millimeter) — Value of 3; (E) Severe edema (raised more than 1 millimeter and extending beyond the area of exposure) — Value of 4. NOTE: The “value” recorded for each reading is the average value of the six or more animals subject to the test. (2) Readings are again made at the end of a total of 72 hours (48 hours after the first reading). An equal number of exposures are made on areas of skin that have been previously abraded. The abrasions are minor incisions through the stratum corneum, but not sufficiently deep to disturb the derma or to produce bleeding. Evaluate the reactions of the abraded skin at 24 hours and 72 hours, as described in this paragraph. Add the values for erythema and eschar formation at 24 hours and at 72 hours for intact skin to the values on abraded skin at 24 hours and at 72 hours (four values). Similarly, add the values for edema formation at 24 hours and at 72 hours for intact and abraded skin (four values). The total of the eight values is divided by four to give the primary irritation score. Exposure times and units: (a) Erythema and eschar formation: (A) Intact skin: (i) 24 hours — Value of 2; (ii) 72 hours — Value of 1. (B) Abraded skin: (i) 24 hours — Value of 3; (ii) 72 hours — Value of 2. (C) Subtotal of exposure unit values = 8. (b) Edema formation: (A) Intact skin: (i) 24 hours — Value of 0; (ii) 12 hours — Value of 1. (B) Abraded skin: (i) 24 hours — Value of 1; (ii) 72 hours — Value of 2. (C) Subtotal of exposure unit values = 8. (c) Total exposure unit values = 12. NOTE: Primary irritation score is 12 divided by 4 = 3. Statutory/Other Authority: ORS 453.095 Statutes/Other Implemented: ORS 453.005 & 453.055 History: HD 40, f. 8-2-73, ef. 8-15-73