286 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE 7--CLASSIFICATION OF COMPOUNDS BASED ON EYE IRRITATION PROPERTIES (STEPS 1 AND 2) Step ! Find the maximum, mean total score for all three tissues occurring within the first 96 hr. following instillation for which the incidence of this score plus or minus 5 points is at least 40 per cent. Step 2 Choose an initial or tentative rating on the basis of the score found in step 1 as follows: Score from step 0.0 to 0.5 points 0.5 to 2.5 points 2 5 to 15 points 15 to 25 points 25 to 50 points 50 to 80 points 80 to 100 points 100 to 110 points Tentative eye irritation rating Nonirritating Practically nonirritating Minimally irritating Mildly ir•'itating Moderately irritating Severely irritating Extremely irritating Maximally irritating For borderline scores choose the higher rating ensure that certain requirements are met before permitting a tenlalive rating (developed from Steps 1 and 2) to become a final rating. In the example cited (Table 5) the tentative rating selected was "moder- ately irritating." This class is symbolized by "M•" in Table 8 and it is seen that two requirements must be met before this tentative rating may become final. The first requirement is that the mean total score for the seven-day scoring interval may not exceed 20 points if the rating is to be maintained. The second requirement pertains to the incidence of the individual rabbit scores. The requirement states that individual total TABLE 8--CLasSIFICATION OF COMPOUNDS BASED ON EYE IRRITATION PROPERTIES (STEP 3) Tentative Rating Requirement for Maintenance N MTS24 = 0 for MTS24 0, raise one level PN As for N M• MTS4s = 0 for MTS4s 0, raise one level M2 MTS90 = 0 for MTSga 0, raise one level Ma (1) MTS _ 20 for MTS 20, raise one level (2) ITSs _ 10 (60%) if not true then no rab- bit may show ITSs 30 otherwise raise one level S (1) As for Ma except use MTSs _ 40 (2) As for Ma except use ITSz _ 30 (60%) and 60 for high E (1) As for Ma except use MTS _ 80 (2) As for Ma except nse ITS• _ 60 (60%) and 100 for high Mx (1) MTS 80 (60%) for MTSf _ 80, lower one level (2) ITS 60 (60%) otherwise lower one level Symbols: MTS = Mean total score. ITS = Individual rabbit total score. Subscripts denote scoring interval: 24, 48 or 96 hr. f = final score (7 days).

INTERPRETATION OF EYE IRRITATION TESTS 287 scores for at least 60 per cent of the rabbits should be 10 points or less and in no case may any individual rabbit's total score exceed 30. If either or both of these two requirements are not met (the one relating to the mean total score and the other to the individual Zola/scores for the rabbits) then the tentative rating must be raised one level and the higher level becomes the final razing. With the above in mind the example cited in Table 5 may now be classi- fied for a final rating. It will be seen at once that the first requirement for maintaining the tentative assignment of "Moderately Irritating" is not fulfilled, namely, the mean total score at the seven-day point exceeds 20 points. Actually it is not necessary to proceed any further and the final rating becomes '•Severely Irritating," the next-highest class. However, it may be noted in passing that the second requirement is also not met. Not only are the individual total scores at seven days for all five rabbits (100 per cent) greater than 10 but the score for Rabbit No. 2 actually exceeds 30. The final rating of "Severely Irritating" more properly describes the irritancy produced by this product than would the phrase "Moderately Irritating." First of all, a high order of irritation was produced during the first hour, the magnitude being over 40 per cent of the theoretical maximum. Secondly, the degree of irritation had not changed noticeably by the twenty-four-hour point and decreased only slowly thereafter. Even at the end of seven days, iridial irritation was still maximum for all rabbits and conjunctival irritation had not dropped even 50 per cent relative to the one-hour value. It is true that corneal scores did drop to practically one-third of the one-hour value and that there was good evidence that no permanent eye injury would result. However, a product producing ir- ritation on this scale and for this time length could scarcely be described as only a "moderate eye irritant." The foregoing, rather detailed analysis has been developed as an aid to both our clients and to ourselves. Although at first sight apparently laborious, familiarity through practice readily enables an investigator to classify irritants quite rapidly, within a matter of seconds for most compounds. The system is by no means foolproof. It has been altered several times in the last few years and will undoubtedly be modified again. It is, nevertheless, a practical, workable system yielding results that enable product inter-comparisons to be made both more quickly and easily as opposed to comparisons of raw eye irritation scoring data. Before proceeding to illustrate the range of eye irritation typical of some general types of cosmetic products, it is worth observing that the test we have been discussing is not to be thought of as one whose results are necessarily the exact equivalent of those which might be expected following actual accidental contact of the test agent with the human eye. The basic test we have discussed is, comparatively speaking, a very strin-