104 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table VI Protective Index Sample Description Protective Index T27-78-3 Amerscreen P 2 per cent in alcohol glycerine water T27-78-4 Amerscreen P 5 lzer cent in alcohol glycerine water 30 T25-268-2 Amerscreen P 5 per cent in Carbopol lotion base 60 T32-64-2 Amerscreen P 5 per cent in Carbowax base 70 T32-56-1 Amerscreen P 5 per cent in oil base 20 were exposed to 20, 40, and 60 times the radiation necessary to produce mild erythcma on untreated skin (20, 40, and 60 MED). The 1.0 and 2.5 per cent propoxylated ethyl p-aminobenzoate lotions are modifications of the 5.0 per cent propoxylated ethyl p-aminobenzoate lotion previously described, with water replacing propoxylated ethyl p-aminobenzoate in the formula. Fifty brg of lotion were applied to 1 sq in. of skin and observed versus untreated skin as a control. A Xenon lamp was used as the radiation source. Only barely perceptible erythema was observed at the highest radiation dose with the 1.0 per cent propoxylated ethyl p-aminobenzoate concentration. Substan.tivity after Bathing To determine whether propoxylated ethyl p-aminobenzoate formulations would still be effective after bathing, 50 brg of lotion were applied tol sq in. test area on the forearms of 6 healthy adult male volunteers. The volun- teers immersed their forearms in an agitated water bath thermostatically controlled at 37øC. After 10 min immersion the subjects were exposed to 6 MED. Results of this immersion test are tabulated in Table VII and indicate that propoxylated ethyl p-aminobenzoate formulations will provide a fair degree of protection even after bathing, but concentrations higher than 1 per cent are recommended for complete protection after bathing. Heat Stability To determine heat stability of propoxylated ethyl p-aminobenzoate, a closed jar of 100 per cent propoxylated ethyl p-aminobenzoate was held at 105øC for 62 'hours. The jar was opened periodically and samples removed to determine changes in uv absorption, chemical composition, color, and odor. Very slight yellowing was detected however, the heated sample was still within normal batch-to-batch variation, and uv absorption, composition, and odor were unchanged. Staining of Fabrics Propoxylated ethyl p-aminobenzoate formulations were tested for staining of cotton and 80/20 cotton-nylon blends. Hydroalcohol and oil preparations containing 2.5 and 5.0 per cent propoxylated ethyl p-aminobcnzoate were ap-

EVALUATION OF SUNSCREENING AGENT Table VII Amerscreen P Immersion Effect 105 1 per cent Amerscreen P Lotion Radiation (MEDS) 2.5 per cent Amerscreen P Lotion Radiation (MEDS) 5.0 per cent Amerscreen P Lotion Radiation (MEDS) Subject 6 6 6 1 2 1 1 2 2 1 0 3 1 1 0 4 2 1 1 5 1 0 0 6 2 2 1 Control 3+ 3+ 3+ plied to the fabrics and exposed to direct sunlight for 5 hours. All formula- tions produced slight yellowing, which was easily and completely removed by mild laundering, while PABA formulations produced a permanent deep yel- low stain. Results are shown in Table VIII. Field Trials Each formula type must be evaluated under actual use conditions to prove efficacy in both sunburn prevention and suntan formation. Field trials were conducted with the following sunscreen butter formulas as is shown in the following table. Amerscreen P* 1.0% 2.0% Solulan© PB-20* 40.0 40.0 Isopropy] palmirate 43.0 42.0 Cande]ilia wax 12.0 12.0 Carnauba xvax 4.0 4.0 Perfume and preservative q.s. q.s. Sunscreen butter is prepared by dissolving propoxylated ethyl p-amino- benzoate in Solulan PB-20 with slight heating. The remaining ingredients are added and the mixture heated to 85øC while it is mixed slowly until it is clear and uniform. Mixing is continued while it is cooled to 35øC, and the formula is then homogenized. The formulas were packaged in tubes and distributed over an 18-month period to more than 25 subjects. The formulas were used in the Swiss Alps at 3000 m and on the beaches of the Bahamas, Southern Florida, New Jersey, and Long Island. No special precautions were taken for initial exposure. All * Amerchol, Edison, N.J. 08817.