A preservative is a substance of natural or synthetic origin intended to inhibit the growth of microorganisms. This inhibition must be effective over a wide range of activities and for a period of time longer than that of the cosmetic product itself, which is equivalent to the expected shelf life plus the time of use. In addition, the antimicrobial activity must be sufficiently effective to prevent the adaptation and resistance of microorganisms to the preservative system.
The Council of the European Union has provided the following definition: “Cosmetic product means any substance or mixture intended to be placed in contact with the external parts of the human body (epidermis, hair system, nails, lips and external genitalia) or with the teeth and mucous membranes of the oral cavity with a view exclusively or mainly to cleaning them, perfuming them, changing their appearance, protecting them, keeping them in good condition or correcting body odors”.
In general, a cosmetic product is used in the direct treatment of the external surface of the human body in order to perform the following four functions: (1) keeping them in good condition; (2) changing their appearance; (3) protection; and (4) body odor correction
Cosmetics can be classified based on their application, application areas, function, preparation type, age or gender of the consumer, and other factors. The most appropriate classification is as follows:
(1) cosmetics for personal cleansing (soaps, deodorants, shampoos); (2) cosmetics for skin, hair, and skin care (toothpaste, external genitalia care products); (3) cosmetics for make-up (perfumes, lip colors); (4) protective cosmetics (sunscreen products, anti-wrinkle products); (5) corrective cosmetics (beauty masks, hair dyes); (6) preservative cosmetics (shaving cream, moisturizers); and (7) active cosmetics (fluoridated toothpastes, disinfectants).
In general, all products, including cosmetics, containing water and organic/mineral compounds under appropriate physicochemical conditions, are subject to microbial contamination.
This justifies why these products require effective and adequate protection against the proliferation of microorganisms. An ideal preservation system (intrinsic or extrinsic) should protect the product from microbial degradation, both in the original packaging until use and in the opened container during use.
Common microorganisms found in cosmetics include Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Candida albicans as well as other bacteria, fungi and yeasts. The skin and mucous membranes are protected from microorganisms. However, their presence in these products can increase the risk of microbial infection. Microbial contamination may occur during production (primary contamination) and/or during use by the consumer (secondary contamination). The diagram in Figure 1 summarizes the causes, consequences and ways to prevent both types of pollution (primary and secondary). In addition, all potential sources of pollution should be identified and monitored. To do this, four stages should be considered: (1) inspection and control of raw materials; (2) the production process; (3) delivery of the finished product and finally (4) its use by the consumer.
Figure 1. Causes, consequences. and ways of preventing cosmetics contamination
With the rapid industrialization and emergence of new ingredients used in cosmetics, several guidelines and regulations have been developed to control the use of these ingredients, ensure consumer safety, determine responsibilities, and allow for litigation regarding adverse effects. Among the important and prominent regulators in the world are the FDA, Japan, and the EU.
The regulations set by these three regulators are as follows:
FDA: For the eye area and products for infants, it should not exceed 500 colony-forming units (CFU) per gram and for other products, it should not exceed 1000 colony-forming units per gram
Japan: The total aerobic microorganism count in products for oral, gingival, cutaneous and nasal use should not exceed 102 CFU/g or CFU/mL and the total yeast/mold count should not exceed 101 CFU/g or CFU/mL in the absence of Staphylococcus aureus and Pseudomonas aeruginosa in 1 g or 1 ml of the product.
EU: In the European Union, two distinct categories of cosmetic products are defined within the scope of microbiological quality control:
Category 1 – Products specifically intended for children under three years of age and used in the eye area and mucous membranes. The total number of mesophilic aerobic microorganisms should not exceed 102 CFU/g or 102 CFU/mL of product
Category 2 – For other classified cosmetics, the total number of mesophilic aerobic microorganisms should not exceed 103 CFU/g or 103 CFU/mL of product.
Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans are considered to be the main potential pathogens in cosmetic products. These specific potential pathogens should not be detectable in 1 g or 1 mL of a Category 1 cosmetic product and in 0.1 g or 0.1 mL of a Category 2 cosmetic product
Microbial preservation strategies cover the entire process from the initial stages of production to consumption to minimize the risk of microbial contamination. To achieve good protection of cosmetic products against microbial contamination, the industry offers two stages of preservation: primary and secondary. Primary preservation strategy is carried out during production and is based on the application of GMP. Secondary preservation, which is carried out after production, uses chemical, physical or physicochemical methods to achieve efficient protection.
Primary preservation strategy: GMP must be strictly observed during the production of cosmetic products. The preparation of cosmetics under completely sterile conditions should prevent their microbial contamination. Water purification, microbial control of raw materials, disinfection of equipment and personnel qualification can reduce the risk of contamination
Secondary preservation strategy: Three main strategies have been used to preserve cosmetic products during storage, transportation and use: physical, chemical and physicochemical preservation.
Physical secondary preservation: This type of preservation is complemented by the use of primary packaging, in which there is a physical barrier to prevent microbial contamination. Two levels of protection can be provided by the packaging:
(1) against contamination during use; and (2) against the accumulation of contamination in the distribution system
Secondary physicochemical preservation: water activity, emulsion form and pH control are among these
Synthetic chemical preservatives: The EU Cosmetics Directive refers to preservatives that are intended exclusively or mainly to inhibit the growth of microorganisms in cosmetic products. Their presence is essential in most cosmetic products. The selection of these preservatives as ingredients in cosmetics must comply with Annex V of the Cosmetics Regulation. In general, the selection of preservatives is based on three criteria (plus regulatory criteria): (1) very good antimicrobial effect; (2) non-toxicity; and (3) compatibility with other ingredients of the cosmetic formulation. Currently, preservatives have been used as mixtures to increase antimicrobial activity, extend the spectrum of activity, reduce the resistance of microorganisms and the risk of toxicity.
In general, an ideal preservative should be stable, compatible, effective at low levels, non-toxic, compliant with cosmetic and health regulations, and inexpensive.
Source: preservative/molecules-23-01571.pdf
