INSUI,T PATCH TESTS IN STUDY OF CUTANEOUS REACTION 249 other hand, no cosmetic, however cheap will succeed on the market if the consumer dislikes its inferior quality. CONCLUSION The use of the new methods of quality evaluation and toxicological pro- tection by the leading cosmetic manufacturers in this country and abroad is an indication that the trend of the industry is in the continuous improve- ment of its products. These methods are being improved almost every day or replaced once in a while by quicker and more accurate ones. Very soon, all obsolete empiric research routines will disappear from all cosmetic laboratories as the cracker barrel has disappeared from the corner grocery. THE CLOSED, OPEN, PROPHETIC AND REPEATED INSULT PATCH TESTS IN STUDY OF CUTANEOUS REACTION By JOSEPH V. KLAUDER* oeresented December 2, 1959, New York City TifF. pro,POSES of the patch test in study of cutaneous reaction are as follows: (1) To determine the range of concentration of a given substance that exerts (under the test conditions) a primary cutaneous irritant action. (2) Diagnostic: to determine if the skin is allergic to the tested sub- stance. (3) To determine if a given substance has allergenic action suflqcient, under the test conditions, to sensitize the skin by several or repeated appli- cations. (4) To determine other untoward cutaneous reactions as later dis- cussed. A primary cutaneous irritant is that concentration of a substance in that degree and duration of exposure that produces an inflammatory cutaneous reaction usually characterized by varying degrees of erythema, with or without swelling or blister formation. Since the irritability or reactibility of the skin varies in different persons, some may react to that concentra- tion to which others did not react as the concentration is increased a greater percentage of persons react until that concentration is reached that all persons will react. I think the proper concept of a cutaneous irri- tant is the reaction of an individual and not that of all persons. A cutaneous allergic substance is one that will produce a cutaneous reaction usually comprising degree of erythema comparable to that of a * Philadelphia, Pa.

250 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS primary irritant to which the normal skin does not react or to that concentration below (at times considerably below) the concentration that produces primary irritant action. Closed Patch Test: The patch test as ordinarily employed is closed-- the tested substance on the skin is covered (closed). If the covering (patch) excludes air it is occlusive if it does not, it is nonocclusive. It should be noted that minimum concentration which produces cutaneous reaction by closed patch test is well below that concentration which produces cutaneous reaction without covering as in ordinary actual use of the tested substance. It should also be noted that some substances which contact the skin in ordinary use without cutaneous reaction may cause such reaction if a closed patch test is performed. This applies, for example, to solution of soap, nonaqueous solvents, some essential oils, some sulfated oils and preparations containing alcohol. This does not apply to substances that are inherently not primary cutaneous irritants like rubber, tobacco, wood. Cutaneous reaction to such substances in closed patch test is an allergic one and not one of primary irritant action as in the aforegoing examples. In diagnosis of cutaneous allergy by closed patch test, it is imperative, to employ that concentration that does not produce primary i• titant action. If that concentration is not known, as a short cut, in performing a series of tests with varying dilutions on normal persons, an open patch test is employed. Open Patch Test: This is placing on the skin a few drops of the tested substance in use concentration or a comparable small amount, if not a liquid, allowing it to remain without covering (means may be taken to prevent its removal by clothing). If the skin is sensitized a positive reac- tion is to be expected. If powerful vesicants or irritants are tested in this manner dilution is necessary. Prophetic Pa/ch Test (Schwartz-Peck): Another purpose of the closed patch test, as aforementioned, is to determine if the tested substance has that degree of allergenicity that will sensitize the skin, by several or re- peated applications. For this purpose the prophetic or repeated insult method are employed. For the prophetic patch test two applications of the tested substance are used, usually on 200 subjects. The first application remains on the skin for forty-eight hours (some advise up to five days not always practical in hot weather). About two weeks later the second application is applied for twenty-four hours. Positive reactions after the first application indicates either primary irritant action or (less likely) that the tested person is allergic to the tested substance. Positive reactions after second applica- tion, if of sufficient severity (I believe more than 1 plus) indicates sensiti-