[Code of Federal Regulations]
[Title 16, Volume 2]
[Revised as of January 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 16CFR1500.41]

[Page 438-439]
 
                     TITLE 16--COMMERCIAL PRACTICES
 
             CHAPTER II--CONSUMER PRODUCT SAFETY COMMISSION
 
PART 1500_HAZARDOUS SUBSTANCES AND ARTICLES; ADMINISTRATION AND 
ENFORCEMENT REGULATIONS--Table of Contents
 
Sec.  1500.41  Method of testing primary irritant substances.

    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 inch by 1 inch and two single layers thick, 0.5 milliliter (in the 
case of liquids) or 0.5 gram (in the case of solids and semisolids) 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 table:

------------------------------------------------------------------------
                        Skin reaction                          Value \1\
------------------------------------------------------------------------
Erythema and eschar formation:
  No erythema................................................          0
  Very slight erythema (barely perceptible)..................          1
  Well-defined erythema......................................          2
  Moderate to severe erythema................................          3
  Severe erythema (beet redness) to slight eschar formations           4
   (injuries in depth).......................................
Edema formation:
  No edema...................................................          0
  Very slight edema (barely perceptible).....................          1
  Slight edema (edges of area well defined by definite                 2
   raising)..................................................
  Moderate edema (raised approximately 1 millimeter).........          3
  Severe edema (raised more than 1 millimeter and extending            4
   beyond the area of exposure)..............................
------------------------------------------------------------------------
\1\ The ``value'' recorded for each reading is the average value of the
  six or more animals subject to the test.


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

[[Page 439]]

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; for example:

------------------------------------------------------------------------
                                                    Exposure
                  Skin reaction                       time    Evaluation
                                                    (hours)      value
------------------------------------------------------------------------
Erythema and eschar formation:
  Intact skin....................................         24           2
   Do............................................         72           1
  Abraded skin...................................         24           3
   Do............................................         72           2
                                                  ----------------------
     Subtotal....................................  .........           8
                                                  ======================
Edema formation:
  Intact skin....................................         24           0
   Do............................................         72           1
  Abraded skin...................................         24           1
   Do............................................         72           2
                                                  ----------------------
     Subtotal....................................  .........           4
                                                  ======================
     Total.......................................  .........          12
------------------------------------------------------------------------


Thus, the primary irritation score is 12/4=3.