120 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS concentration of the germicide. Al- though no definite relationship ex- ists between surface activity and germicidal potency of these cationic surfactants, their effect on cells is primarily physical, rather than chem- ical as is the case with halogen- liberating compounds (5). These germicides are effective against a variety of micro/Srganisms. Certain bacteria, notably cocci, are more susceptible than gram negative species of the coliform groups. Such skin pathogens as the micrococci and streptococci are readily killed by dilutions ranging from 1-20,000 to 1-100,000. Oral bacteria, such as Neisseria catarrhalis, are killed by dilutions ranging up to 1-300,000. Coliform types, as Escherichia, Sal- monella, and Shigella require from 1-10,000 to 1-30,000. The pathogenic fungi are gener- ally more resistant to quaternaries than are the pathogenic bacteria. Concentrations of 1-500 to 1-2500 are effective against the causative organisms of such skin and scalp mycoses as athlete's foot and ring- worm. The phenol coefficient procedure has been widely used to determine the activity of germicidal sub- stances. However, it is not generally applicable to cosmetic preparations inasmuch as most of these are used in undiluted form whereas this pro- cedure determines the maximum dilution of the product capable of killing in ten minutes. Further, the physical nature of many products prevents their uniform dispersion in the medication mixture. As in other fields, judgment of the antimicrobial and clinical value of a preparation should be based on tests simulating use conditions. These should involve application for extended periods of time to a sub- strate resembling the human skin. Preliminary evaluation of antiseptic activity is usually made with agar plate and broth tube inhibition tests. It h.as been demostrated that as little as one part of quaternary in two million parts of medium may exert antiseptic activity in broth while higher concentrations are re- quired in plate tests because of ad- sorption by the agar. Unfortun- ately, it is not possible to make a simple estimation of the value of several types of preparations be- cause of the lack of suitable test procedures (6). Antiseptic activity should also be determined in the presence of ad- ditional interfering substances. Al- though blood and serum are not pres- ent on normal skin, these substances are often incorporated into test media in order to determine whether the preparation is effective under adverse conditions. Quaternary preparations retain from 20 to 50 per cent of their activity in such tests. ToxicITY The toxicity of quaternary am- monium germicides to man and ani- mals has been determined by several routes of administration. The acute oral dose required to kill one-half of test animals fasted overnight ranges from 250 to 1000

AMMONIUM COMPOUNDS IN COSMETIC AND RELATED PRODUCTS 121 milligrams per kilogram body weight depending on the type of compound and test animal. In chronic studies, substitution of 1-1000 solution for the drinking water of mice, rats, and chickens has not reduced activity, the rate of growth, nor produced toxic reactions. Similarly, the in- clusion of as much as one part of quaternary in 400 parts of the diet of rats has caused no apparent toxic symptoms nor induced pathological conditions in vital organs (7). The tolerance of high concentra- tions in drinking water and food, as compared to the effect of single large doses to fasted animals, is probably due in part to removal of the ger- micide from solution by adsorption on food substances. These com- pounds are highly water soluble, aiding their excretion from the body. Antiseptic concentrations of qua- ternaries are not irritating to human skin. Solutions containing 3 per cent of several of these compounds have been applied to human skin for forty eight hours without causing irritation. Solutions containing 10 per cent or more produce varying degrees of erythema. Repeat tests show absence of sensitization prop- erties (8). Because of the possibility of acci- dental introduction into the eye, consideration must be given to the effect of corneal tissues. Various investigators have reported no irri- tation at concentrations ranging from 0.02 to 0.2 per cent, depending on the test compound and duration of exposure. It may be concluded from tests conducted according to the procedure of Draize that con- centrations ranging from 0.5 to 1.0 per cent are not permanently in- jurious to the eye (9). Mucous membranes of the oral and vag- inal cavities are slightly less sensi- tive. The extensive use of quaternary ammonium germicides in pharmaceu- tical and cosmetic products has demonstrated their safety and ef- fectiveness when properly used. Several compounds are generally not considered to be "new drugs" and have been accepted in official com- pendia. However, each new ap- plication and new combination of substances should be tested for safety and effectiveness before it is offered for sale. PRACTICAL APPLICATION With due consideration for the factors of safety and compatibility, quaternary ammonium compounds may be added to most cosmetics to provide antiseptic, deodorant, and keratoplastic properties. The choice of compound and concentration employed depends on the type of product, the manner in which it is to be applied and effect desired. Some examples will be given. Antiseptic tinctures for treatment of minor wounds and preoperative preparation may contain up to 3 per cent quaternary, alcohol, ace- tone, water, and a dye to delineate the area of application. Solutions for bathing traumautized areas us- ually contain 0.1 per cent quater- nary and may be buffered near neutrality. Ophthalmic solutions