USE OF ANTI-IRRITANTS IN COSMETIC FORMULATING 333 the conclusion that certain materials can act as potent anti-irritants for others. Furthermore, ingredients may change roles, varying from ir- ritant to "safe" to anti-irritant, depending on what other materials are used in conjunction with them in a formulation. No material should ever be considered absolutely safe or absolutely unsafe for application to the human body. Safety data on individual ingredients are very useful (giving an indication of problems which may arise), but no formulator should depend solely on so-called positive and negative lists of permitted or forbidden ingredients. Someone once said, "Wisdom would be easy if we only had to choose between the black and the white." Unfortunately, the cosmetic for- mulator is rarely offered a clear-cut choice in trying to decide whether a particular product will be "safe" when used by the general public. The cosmetic formulator must do the best he can with test data of the sort currently available to him, resulting from applying the .finished product in the manner intended for use by the ultimate consumer. This gives him the greatest possible flexibility and allows the use of any ingredients he chooses, so long as he can show that the final product is not inju- rious. APPENDIX Following is a list of two dozen cosmetic ingredients for which reasonably credible anti-irritant claims have been made. Reference to the original published data is strongly recommended to those interested in using these products as anti-irritants. Not all of the claims have been rigorously substantiated. Regardless, confirmatory irritation testing should always be carried out on finished formulations even though they contain materials previously shown to possess anti-irritant properties. Inclusion in this list does not constitute general endorsement. In- stead, it is hoped to bring these materials, and the claims made for them, to the attention of cosmetic chemists for further investigation of possible anti-irritant activity. Aloe Vera Several references (17, 18) claim remarkable curative and detoxifying powers (topical and internal) for the hexosan gel and other polyuronide extracts of thi. s cactus. They also claim topical anesthetic effects and (17, 19) promotion of healing (granulation) of damaged tissue. No published data are available proving anti-irritant activity in controlled tests.

334 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Allantoin Several dermatologists have been reported by Mecca (14) to have shown that aluminum allantoinates enhance antiperspirant action of other aluminum salts while reducing their irritation potential consider- ably. Kahan and others (15, 16) have reported that 0.2% allantoin in creams or talcums help prevent diaper dermatitis (generally considered to be caused by ammonia liberated from the urine). The author observed (of. preceding pages) that addition of all antoin to lipsticks containing bromo acids made them tolerable to women who could not otherwise use them. In contrast, it was shown in the pre- ceding pages that addition of 0.25% aluminum chlorhydroxy allantoinate to an antiperspirant containing both aluminum chlorhydroxide and a quaternary antiseptic increased eye irritation, perhaps due to activation of the cationic agent. A nion- Cation Complexes Use of equimolar mixtures of anionic and cationic surfactants in certain shampoo compositions (which contain substantial amounts of amphoteric surfactant) is claimed by Goff (20) to result in preparations which foam well and leave the hair in good condition. The amounts of eationic recommended (up to 4.9%) would normally be extremely irritating to the eye. Eye irritation is not discussed in the patent, but it must be presumed that the anti-irritant activity of the amphoteric is greatly helped by neutralizing the cationic via "complexation" with the anionic surfactant. A ryloxypropionates A rather well documented paper by Northover and Subramanian (21) shows that formaldehyde-induced inflammation can be inhibited by a number of these substances, some of which will also inhibit reaction to intradermal injection of histamine. Cortisone acetate was inactive. This study did not involve cosmetic ingredients and was performed via intradermal techniques rather than topical application. Neverthe- less, it may have considerable application to cosmetics. Azulene Ruemele (22) used a large quantity (0.25%) of 1,4 dimethyl-7 isopropyl azulene in an unspecified alkaline depilatory formula which was routinely applied to the face as well as arms and legs. He claims distinct anti irritant action but offers no data to prove it. It was shown