TESTING ANTIACNE AGENTS IN DOGS 475 Preparation Tested Table I Effects of Materials Applied on the Skin of Mexican Hairless Dogs _ Conc. Vehicle Conc. Description • (%) (%) Cleaner Salicylic acid 3 Propylene 100 q-/- glycol ...... Propylene ... -- glycol Salicylic acid 2 Alcohol 70 q- Hexachlorophene 1 Water 30 ...... Above ß ß ß -4- vehicle Benzoyl peroxide 10 AltohoP' 40 Cellosolve 40 Propylene 20 q- glycol ...... Above ... q- vehicle Vitamin A acid 0.1 Alcohol 70 Propylene 30 q- glycol ...... Above ... +/- vehicle Drying, Flaking Comedone Irritation Extrusion Removal JI- + +/- + -- +/-- q- ++ + +++ +q- aCode: --, none +/--, questionable +, slight q-+, moderate 4'-4-+, marked. •Suggested by Fulton (12). void of activity. Alcohol-containing vehicles produced a slight cleansing and also resulted in drying or flaking of the treated areas. Cleansing of the treated sites, when observed, was attributed to the activity of these vehicles. Tissue sections of these control sites yielded no evidence of irritation. Su- perficial and deep fo]licular structures were consistently filled with keratin which confirmed the inability of the vehicle treatment to cause comedone loss. Salicylic acid, alone or with hexachlorophene, produced drying of the treated areas. No irritation was produced by these preparations. Minimal overt evidence of keratin extrusions from follicular sites was observed and was confirmed histologically. Benzoyl peroxide treatment resulted in slight keratin extrusion from folli- cular sites which was accompanied by slight erythema as observed grossly. Histologically, evidence of minimal to moderate epidermal parakeratosis was seQn.

476 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 1. Appearance of plugged follicles (site to be treated is within four marked spots) Figure 2. Effects produced by vitamin A acid (same site as in Fig. 1)