USE OF ANTI-IRRITANTS IN COSMETIC FOI4MULATING 327 For this reason, the ()/W emulsion was chosen, even though it appeared more irritating. It was hoped that an anti-irritant could be found which would not affect the enzyme stability, yet prove helpful in reducing primary skin irritation. Three additives-were investigated' sodium lactate, a combination buffer-humectant normally produced by the body and present on the skin glycogen, demonstrated by ()pdyke (13) to be present in "accommodated skin" which no longer reacts to irritants and the previously discussed thiodig'lycolic acid. The results of this rather limited test are shown in Table III. Quite clearly, addition of the protease did not increase the irritation potential of either vehicle. Addition of glycogen or sodium lactate to the O/W proteolytic emulsion made it considerably more irritating. Addition of 0.3% thiodiglycolic acid reduced its irritation by what may be a significant amount. This small test should be confirmed by using higher levels of thiodiglycolic acid and on a larger group of subjects. A Shampoo Problem The creation of a safe high-foaming concentrated gel shmnpoo is a typical example of a formulator's nightmare and will illustrate the difficulties encountered during the development of cosmetic products. The basic formulating problem is quite "simple," and acceptable laboratory batches of gel shampoos can be formulated readily. How- ever, it soon becomes apparent that formulations containing detergent might be irritating to the eye. The formulator then starts irritation testing of his product, using leading gel shampoos as controls. He quickly learns that his "simple" product is a severe eye irritant and cannot be marketed safely. The "active" ingredients of his formula are 20% triethanolamine lauryl sulfate (TLS) and 5• monoethanolamine "super amide" of coconut fatty acids (MEAC) (Fig. 1). Unfortunately, these ingredients are far "too active" when the gel is instilled pure into rabbit eyes, with the seventy-two-hour readings showing considerable corneal opacity and some iritis. At this point, the formulator recognizes that solid gel shampoos are quite unlikely ever to enter the eye undiluted. The eye irritation test is, therefore, repeated on a 50% dilution. This reduces corneal and iris damage by one-half (Fig. 1), but the product is still considered to be too irritating. Addition of 1% PVP-K30 to the gel shampoo also reduces irritation by one-half, but the best results are obtained by adding 1% PVP-

328 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS K30 and also diluting the shampoo by 50% (Fig. 1). This reduces eye irritation almost to zero and yields a salable liquid product and plans are promptly made to go into full scale production. Unfortunately, just before full scale production is scheduled to begin, somebody in the laboratory gets nervous and decides to repeat the eye irritation test. The final pilot batch, containing raw materials about to be used in the first full-scale production batch, provides the Base•t5% MEAC• Clear Gel \20% TLS/ 20-10-39 add 1% PVP r 5-5-17 I dilute I dilute 50% 50% 10-5-31 add 1/2% PVP r 0-0-2 Then • Repeat (4 months late•r-ready I 10-2- 25 t dilute 5O% 'further (Product too dilute to sell) 1.25% MEAC') 5.00% ILS / J =Saleable Liquid Shampoo [ 2.5% MEAC\ •10.0% TLS J •0,5% PVP / for production) I add 1/2% PVP • 5-0-17 2.5 % MEAC• 0.0% TLS ! 1.0% PVP-/ Figure 1. Illustration of the development of a gel shampoo. Numbers in boxes are 72-hour Draize test scores of rabbit eyes (unrinsed) in the order, cornea-iris-total points sample for this retest. As can be seen in Fig. 1, retesting for eye ir- ritation produces entirely different results. The shampoo considered salable four months ago now requires reformulation through addition of more PVP or by dilution with water. The latter modification yields an unsatisfactory product. Thus the shampoo with 1% PVP--with some rabbit eye irritation--is the one selected for sale on the assumption that it will be diluted at least 50% before accidentally entering the eye. Developing an A ntiperspirant Formula Antiperspirants present many special problems in terms of skin and eye irritation. They are routinely applied to portions of the body which are usually moist, warm, and subject to constant chafing. They must be quite "active" in order to satisfy the consumer and this same ac-