HYGIENIC MANUFACTURE AND PRESERVATION 771 they may exhibit spoilage owing to the difficulties experienced in cleaning these packaged components effectively before the product is filled. Creams and lotions generally need to be protected against attack by moulds, yeasts, aerobic and anaerobic bacteria by means of a suitable pre- servative. Organisms of particular concern from the public health aspect and which are most likely to be present as contaminants are Pseudomonas aeruginosa, Klebsiella species, and coagulase-positive Staphylococcus aureus. The dark pigmented fungi, such as Cladosporium and coloured moulds, can be a particular nuisance since they so obviously disfigure the product. Although they do not present a serious public health hazard, they could possibly serve as allergens. Anionic detergents in many shampoos are particularly vulnerable to bacterial decomposition. Shampoo prepared from such materials must be protected against gram-negative bacteria generally, and Pseudomonads in particular. Preparations intended for application to or near the eye such as solid or liquid eyeliners, eyelash materials, and pigmented materials for make-up around the eye require particular attention. These preparations should be sterile at the time of manufacture and should also contain a preservative known to be bactericidal to Pseudomonas aeruginosa. Similar precautions are necessary for products to be used on newborn infants or for application to broken skin. Powders, such as raw talcs and mineral earth pigments, may contain large numbers of fungal spores, aerobic and anaerobic bacteria including Clostridial spore-bearing species when used for cosmetic purposes they may need to be subjected to an efficient form of presterilization. Reliance, in this connection, should not be placed on the incorporation of a preserva- tive. 4.2 Recommendations A preservative should always be regarded as an additional aid in pro- longing the shelf-life of a product. It must never be used to mask deficiencies in hygiene. In the avoidance of spoilage, good housekeeping is essential to cosmetic manufacture just as it is to food production. Notwithstanding good manufacturing conditions, unforeseen and exceptional contamination may occur during routine manufacture which will overwhelm an in- adequate preservative system and render it ineffective. The preservative capacity of a product should therefore exceed the minimum requirements

772 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS necessary to inhibit or destroy anticipated levels of microbial contamination. The problem of product spoilage may be exacerbated by using antimi- crobial agents which are themselves susceptible to contamination. Disin- fectants and antiseptic solutions are sometimes metabolised by opportunist bacteria. This situation can result in an unexpected public health hazard instances have, in fact, been recorded where clinical infections have been caused by a contaminated solution of an antibacterial. Given the opportun- ity, bacteria will often show a remarkable ability to adapt to a hostile environment. Antimicrobial compounds used in industry today offer varying degrees of preservative action, depending upon such factors as pH, type of emulsi- fier, micellar solubilization, ease of migration into the oil phase of an emulsion system. There is still an unsatisfied need for the ideal antimicro- bial agent that will remain in the aqueous phase of such systems, where microbial contamination is most likely to reach significant levels, con- tinuing to exert biological activity over a broad pH range and throughout prolonged storage. The antimicrobial agent should be effective against a broad spectrum of micro-organisms, especially against the gram-negative bacteria which are most frequently involved in bacterial spoilage problems. Highly potent antimicrobial agents have sometimes proved to be ineffective as cosmetic preservatives whereas compounds with much weaker inherent antimicrobial properties have been quite effective in these compositions. Certain preservatives with good antimicrobial activity are liable to cause irreversible physical or chemical changes in a product and are therefore useless in practice. Choice of a suitable preservative in adequate but non-toxic concen- tration can usually be made only after considerable experimental work. Consideration of preservatives should therefore be regarded as an integral facet of the initial formulation activity. Decisions should preferably be reached after close collaboration between the formulation chemist, packag- ing technologist, physical chemist, pharmacologist, and microbiologist. Safety, compatibility, effectiveness and cost are the over-riding factors influencing the choice of a particular preservative. If the preservative is a new one or used in unusually high concentrations, data to confirm safety- in-use will be required the risk of sensitizing the skin must also be taken into account. 4.3 List of preservatives This glossary discusses some of the more important antimicrobials which