USE OF ANTI-IRRiTANTS IN COSMETIC FORMULATING 319 draw too near. Formulators must not be tempted to practice healing, and (except for testiug purposes• their business is not primarily the art of applying cosmetics to the hmnan integument. Their proper concern is the preparation of products which are both efficacious and safe to USe. Unfortunately it is sometimes difficult. to prepare prcducts which have both of these properties. By definition, topical preparations which produce more than mere cosmetic effects are said to "have activity." This activity often results from their ability to react with that portion of the body to which they are applied. Both in theory and in fact, therefore, the more "active" a product the greater is the likelihood that it may be either a primary irritant or a skin sensitizer. Although long experience may eventually prove an ingredient per- fectly safe, the cosmetic chemist may be somewhat concerned the first time he tries it. Many formulators therefore routinely include "soothing" ingredients in vehicles intended as carriers for such active agents, in order to forestall possible primary skin or eye irritatiop. Their premise is reasonable. They assume that a material which is itself soothing to irritated skin will also act as an anti-irritant when combined with such active ingredients. Often, however, inexperienced workers use such anti-irritants without checking two factors: (a) Does it actually reduce irritation, measurably and substantially ? (b) Does it function without unduly reducing the efficacy of the active ingredient ? Unless a proposed anti-irritant fulfills both of these conditions, there is no point to using it. It would be more logical simply to reduce the total quantity of active ingredient in the formula. Many workers are convinced that inclusion of protective colloids is helpful in reducing the irritation potential of certain types of cosmetic formulas. Others feel that aqueous solutions of irritants are rendered less irritating by emulsifying them with oils. Finally, some believe that it is possible to "complex" certain irritants in such a way that they still retain their useful properties, yet are no longer irritating. Each of these beliefs can be dramatically justified in certain special cases. No one questions the fact that certain bases are "safer" than others when used as vehicles for applying irritants to the skin. Un- fortunately, however, although extravagant claims are made for many ingredients, rigorous proof of anti-irritant activity is almost nonexistent today in the literature.

320 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS A major purpose of this paper, therefore, is to present irritation test data showing specific anti-irritant activity, or lack thereof, for a number of agents which have been claimed to possess this property. The use of such adjuncts is becoming ever more important in formu- lating cosmetics and toiletries. Many countries are now adopting laws which will circumscribe the ability to formulate freely. Since these laws result primarily from increased governmental concern over the safety of cosmetic products, it is evident that we need to know whether certain agents can serve as anti-irritants, so that they can be used with assurance when the need arises. DEFINITIONS AND MECHANISM OF ACTION For purposes of this discussion, an anti-irritant is not merely a material which is soothing to the skin or which helps heal already existing skin irritation. Neither is it simply a lubricant film or coating of powder or cream which reduces frictional (chafing) skin irritations. Broadly defined, an anti-irritant is an agent which, when used in conjunction with skin or eye irritants, reduces their irritation potential suj•ciently so that they can be tolerated when applied to the body. Does this include all anti-inflammatory agents? No. Even though such activity is evidently beneficial and often may be desirable, anti- inflammatory activity per se cannot reduce opacification of the cornea nor prevent degradation of other tissue by corrosive agents. The fact that certain agents act as topical anesthetics is sometimes a "fringe benefit" if they are also anti-irritants. This quality alone however, does not make them anti-irritants. In one classic case (4), the inadvertent use of a mildly anesthetic wetting agent (in a per- manent wave neutralizer) resulted in increased eye irritation for the simple reason that, feeling no pain, users who accidentally introduced the product into their eyes made no effort to rinse it out. Occlusion of the skin by lipophilic materials can prevent irritation caused by aqueous irritants if they are thereby prevented from contact- ing it. Combining the two is not always beneficial, however. A lipophilic film-former can increase irritation if it forms an oc½lusive layer over the irritant and holds it in better contact with the skin. These exceptions merely point up the fact that anti-irritant activity is usually quite specific. The agent which works well in conjunction with one irritant may work poorly or not at all with another. Formation of physical or chemical barriers to prevent the irritant from contact- ing the skin is only one way by which anti-irritants can confer protection.