STINGING CAPACITY OF APPLIED SUBSTANCES 201 merely a reflection of the fact that more females had light complexions. Weigand and Mershon (6) evaluated tear gas (0-chlorobenzylidene malononitrile) for irritancy and stinging in various body regions of black and white subjects. They too found that on the cheek and retroauricular areas, stinging was weaker in blacks and appeared later. II, COMPARISON BETWEEN "STINGERS" AND "NONSTINGERS" ADP (5 per cent), dimethylphthalate (50 per cent in ethanol), propylene glycol (neat), and phosphoric acid (5 per cent) were applied during sweating to 5 lactic acid-positive and 5 lactic acid-negative persons, "stingers" and "nonstingers," respectively. The results are given in Table I. Every stinger experienced moderate to severe stinging with all 4 test agents while stinging was virtually absent in the lactic acid-negative group, except for reduced reac- tions to phosphoric acid at 2 to 5 min. Five per cent ADP mainly produced delayed stinging, while 50 per cent dimethylphthalate caused strong transient stinging as well. IIl. INFLUENCE OF SWEATING A 5 member panel was tested with 5 per cent ADP in ethanol at room temperature. Tests on separate occasions were conducted ar 5, 15, and 30 min after entering the en- vironmental chamber. Stinging did not occur at room temperature. However, stinging was already weakly evident when the application was made 5 min after entering the chamber, before sweating was at full flow. After 15 rain, all 5 subjects experienced intense stinging at the 5-min reading. Rinsing the face with water without leaving the chamber was not followed by an immediate decrease in intensity stinging persisted at the same level for about 10 min, fading to insignificance about 20 rain after removal. IV. ANHIDROSIS The critical role of sweating was further demonstrated by testing skin that has been rendered anhidrotic. Sweating was completely suppressed on 1 cheek of 3 stingers by applying an occlusive patch of 5 per cent aqueous aluminum chloride hexahydrate for 24 h. Three h after removal of the patch, a 5 per cent ethanolic solu- tion of ADP was applied to both cheeks after the subjects had been sweating for 15 min. Stinging was markedly reduced on the anhidrotic side the score was never greater than 1 compared to 3 on the sweating side. V. MULTIPLE APPLICATIONS VERSUS 1 APPLICATION We compared the intensity of stinging with 1 versus 5 applications of 5 per cent lactic acid and 5 per cent ADP in separate groups of 3 stingers each. The test material was ap- plied to 1 side every 5 min for a total of 5 applications starting after the subject had been sweating for 10 min. The opposite side received 1 application at the time of the fifth application to the opposite cheek.

202 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The results were most dramatic with lactic acid. The intensity of stinging increased with each application producing almost intolerable discomfort in all 3 subjects. These hardy volunteers and it was only by dint of much persuasion that the test was corn- pieted. Indeed, superficial erosions subsequently developed in 2 of the 3. Signs tation have never been observed with 1 application. The same pattern of progressive intensification of stinging was observed with ADP, but the severity was less. VI. PRIOR DAMAGE - A. Sunburn.' Using fluorescent sunlamp tubes* 2 MEDs were given to 1 cheek of stingers. The next day stinging was assessed on both sides by applying 5 per cent nolic ADP after 15 rain of sweating. Stinging began earlier and was considerably more intense on the sunburned side in all 3 subjects. An inflammatory reaction thus accentuates the response. B, Chemical irritation.' A 5 per cent aqueous solution of a quaternary ammonium pound• was applied to 1 cheek by occlusive patches for 10 rain twice daily for 2 days• •.•5 :• Five per cent ADP was applied.to both cheeks of 3 sweating stingers one day later•:•? when the treated skin showed moderate erythema and tiny pustules. Stinging was sharply accentuated on irritated skin, emerging more rapidly and ing very intense after a few minutes. : VII. STINOING ON STRIPPED SnN A. Lactic actd.' The cheeks of 3 nonstingers were scotch-tape stripped to the ghsten-5• ing layer while half that number of strippings was made on the other side. After subjects had been sweating for 15 rain, 5 per cent lactic acid was applied to both'•3• cheeks. Stinging appeared immediately and in high intensity on the completely stripped side,•(• Stinging was less on the partially stripped opposite side, but was nonetheless apprecia2•'• ble. The duration on stripped skin was shorter than on the normal skin of"stingers.•.• The stinging on completely stripped skin was very sharp upon application, but within 2.5 min. This result indicates that all persons will experience stinging after moval of the horny layer barrier. In another test, 5 per cent lactic acid was applied to the stripped skin of the nonsweatS•:•3• ing back of 3 stingers and 3 nonstingers. Stinging, indeed pain, was equally intense both groups immediately after application, declining rapidly within a few minutes. Dis'fS• crimination is lost on stripped back skin. B. ADP: A panel of 3 nonstingers was scotch-tape stripped to the glistening layer o n cheek and 1 side of the upper back. Five per cent ADP was applied to both normal *Westinghouse FS 20. *Hyamine 3500, Rohm & Haas Co., Spring House, PA 19477. : .•:•: