9,72 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS hypothetical man who sprays an entire can of an aerosol insecticide into a small room and then, without opening any windows, goes to sleep in the room rising later he finds manifestations of a contact allergy. Yet he probably would not have treated a can of gasoline that way, despite the relatively innocuous nature of the chemicals in the can of gasoline. TYPES OF AEROSOL TOXICITY Toxic reactions to aerosols have been reported in the literature for several categories of products: cosmetics, such as hair sprays (1-3) and deodorants (1, 4, 5) perfumes (6) personal products such as feminine hygiene deodor- ant sprays (7, 8) and household products, such as spray paints (9), insecti- cides (10), aerosolized vegetable oils (11), and room deodorizers (5, 9). Medicinal aerosols have also been reported to produce some of the same toxic effects, but they will not be discussed in this paper. The types of toxicity reported can be broken down into two main categories, those due to the propellants and those due to the active or inert ingredients in the formula- tions. Propellant toxicity can result either from the refrigerant properties of the propellants (freezing of tissues or local anesthesia) or from the chemical na- ture of the propellants and the biological responses they elicit (12). Many of the reported cases of aerosol toxicity are likely due to toxic reac- tions to the active or inert ingredients in the formulation, rather than to the propellants. Allergic reactions are among the more COlnmon forms of toxic responses to cosmetic aerosols. It has been estimated that approximately 10% of the population as a whole has some type of allergic disease (6) or has suf- fered an allergic response to some foreign substance during their lifetime and it is a well-accepted medical fact that people who are allergic to one sub- stance, or have an allergic disease such as asthma or hay fever, are prone to be allergic to other products as well-especially upon repeated exposure. The incidence of persons allergic to cosmetic products, on the other hand, is probably between 2 and 3%, when verified by a patch test (6). In the data compiled by one cosmetic company who markets a broad range of products, only 448 reactions were reported in 114 million units sold (6). In an earlier reference, the incidence of allergic skin reactions to lanolin was 1.14% in an unscreened sample of users. (Lanolin is widely used in cosmetic formulations for its unique cmollient and emulsification properties.) On the other hand, when a controlled sample with no history of allergic skin disease was tested, no allergic reactions to lanolin were reported (13). Recent refinements and improvements in the purification of the lanolin used in cosmetic products have eliminated lanolin allergy as a significant problem. Reactions to perfume oils, a ubiquitous ingredient in cosmetic aerosol products, are almost entirely due to an allergic or hypersensitive response, rather than due to primary irritation (6). There are more than 5000 odiferous substances in general use

CURRENT PERSPECTIVES ON AEROSOL TOXICITY 273 today as perfumes. Most cosmetics contain approximately 0.5% perfume oil colognes about 4% and perfumes up to 20%. Each of these perfume sub- stances may contain up to 50 different chemical ingredients, so the task of identifying the cause of an allergic response is, at best, a difficult one (6). Photosensitization is a type of allergic response and has been reported for a number of essential oils, such as neroli, pettigrain, cedarwood, lavender, and bergamot (6, 14). In addition, dermatitis has been reported following the use of oil of bergamot. Chlorophyll, traces of copper, and psoralens, all found in oil of bergamot, are suspected of being the cause of the allergies. Aging of the oil reduces its sensitizing propensity (6). Even once the allergy-causing ingredient has been found, the problem of cross-sensitivity may arise. Persons allergic to oil of citronella, for example, are also often allergic to lemon oil (15). A partial solution to the problem of allergy to perfume oils may have been found with the marketing, by a number of companies, of a group of chemical- ly-reproducible perfume substances which have been patch tested to prove a low incidence of allergic responses (16). Hypoallergenie cosmetics may be another soIution. These are a group of cosmetic products, marketed by a few companies, which are specifically for the use of individuals hypersensitive to many cosmetics. The raw materials for these products are selected on the ba- sis of a reported low incidence of allergic responses (6). The pyrethrins, found in many insecticide aerosols, may also cause a variety of allergic manifestations in susceptible individuals erythema, rash, loss of feeling in exposed parts of the skin, and diminished vision have all been re- ported (10). Another type of toxicity, though less important, that may result from the active or inert ingredients in many cosmetic aerosols, is primary irritation of the skin (17). This is not an allergic response but rather is a result of the caustic nature of certain ingredients in the formulation. Calcium thioglycolate is a primary irritant found in many aerosol foam depilitories (6). Antiperspir- ants often contain salts of zinc, zirconium, or aluminum which can cause primary irritation (6). Ocular irritation from dandruff shampoos has been reported (18, 19), probably as a result of certain zinc salts. EFFECT OF AEROSOLS ON ANATOMY AND PHYSIOLOGY OF THE SKIN AND RESPIRATORY SYSTEM The underlying cause of many of the toxic reactions resulting from the use of cosmetic and household aerosols seems to be the result of an alteration in the basic anatomy and/or physiology of the skin and respiratory systems. The type of alteration produced depends, to a degree, on the product in question and the area of the body it comes in contact with. Alterations in skin pH are thought to be the basis for the primary irritation produced by the depilitories in foam aerosols. Preparations containing calcium fifioglycolate, for example,