Lecture
Recently, there has been a steady trend toward the use in
cosmetics of products with a high content of the aqueous phase (moisturizing creams,
cosmetic lotions, cosmetic gels, etc.). At the same time, cosmetic products with a high content of the aqueous phase, protein and natural lipid components and extracts are a favorable environment for the development of microorganisms, which can cause purulent diseases of the skin and mucous membranes (cultures of Staphylococcus aureus, Pseudomonas aerugin
Proteus vulgaris) or spoilage of finished products (mold fungus cultures,
fungi of the genus Candida).
Preservatives – are components of cosmetic products necessary for their
long-term storage. The main purpose of introducing preservatives into cosmetic
preparations is to protect their components from microbiological damage .
Preservatives in cosmetic products often cause
various skin lesions (rash, edema and itching). The number of people complaining
of allergic skin reactions has been steadily increasing in recent years.
The range of preservatives used in cosmetics is quite
wide. Annex VI, Part I of Directive 76/768 EEC regulates the use of 47 main preservatives from various classes of chemical compounds. Not all
of them have found widespread use in the cosmetic industry.
For example, in the USA, 11 main preserving agents are used to preserve more than 85% of cosmetic products: nipagin (methylparaben),
nipazol (propylparaben), germall 115 (imidazolidinyl urea), germall II
(diazolidinyl urea), dowicil 200 (a quaternary ammonium salt of urotropine
with cis-1,3-dichloropropene), formaldehyde, butylparaben, bronopol (2-
bromo-2-nitropropane-1,3-diol), sorbic acid and its salts, dehydroacetic
acid and its salts; benzoic acid and its salts. A similar pattern of preservative use has developed in the EU countries. For comparison, it is worth
noting that in Ukraine, formaldehyde, dimol-P (a mixture of 1,3-dimethylol-5,5-dimethylhydantoin, 5,5-dimethylhydantoin and a bis-quaternary ammonium compound),
nipagin, nipazol, bronopol, Kathon CG, irgasan DP300 (2,4,4-trichloro-2-
hydroxydiphenyl ether), germall II, germaben II (a mixture of germall II, methylparaben, propylparaben and polyethylene glycol), triclosan, benzoic
acid and its salts are widely used for preserving cosmetic products .
Today there is no universal preservative. Cosmetics usually
use mixtures of several preservatives. Let us note that practically all
preservatives, when improperly dosed, can have a toxic effect.
Most preservatives, at the concentrations recommended for their use, do not exhibit skin-irritating, skin-resorptive or sensitizing properties. That is, they are characterized by sufficient
safety for the consumer when used in cosmetic products.
To prevent adverse effects of preservatives on the consumer's
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body, Directive 76/768/EEC established limits restricting their
addition to cosmetic products (Table 4.2).
Table 4.2 – Restrictions and requirements for the use of preservatives in the
cosmetics industry
Preservative name Maximum allowable concentration, %
Benzoic acid and its salts 0.5 (as acid)
Bronopol 0.1
Germall II 0.5
Germall 115 0.5
Germaben II 1.0
Dimol-P 1.0
Dowicil 200 0.2
Kathon CG (mixture of 5-chloro-2-methyl-4-
isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, magnesium chloride and
magnesium nitrate)
0.0015 (for the mixture in a ratio
of 3:1 of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one
Parabens
0.4 (as acid) for a single compound; 0.8 (as acid) for a mixture
of compounds
Sorbic acid and its salts 0.6 (as acid)
Triclosan 0.3
Formaldehyde and paraformaldehyde 0.2 (except for oral
care products)
Toxic effects have now been established for such preservatives as
methyldibromoglutaronitrile, isothiazolinones, and compounds that release
formaldehyde upon decomposition, as well as parabens. In some European countries,
especially in Scandinavia and Germany, formulations using so-called "gentle" preservation technology with "natural" preservatives, such as sorbic acid, are becoming increasingly widespread.
Preservatives based on methyldibromoglutaronitrile.
Methyldibromoglutaronitrile (4.3) is often used to prevent the growth of fungi and bacteria in cosmetic products.
It has been established that this preservative causes allergic reactions in people
with eczema. At the same time, even healthy people are also at
risk. In 1991, a reaction to this preservative was observed in only
0.7% of eczema patients. However, by 2000 this figure had risen to 3.5%. This
substance causes redness and irritation of the skin of the scalp, neck and hands – in
places where cosmetic products are mainly used.
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According to the European regulatory framework for cosmetic products
(Directive 2003/83), the use of methyldibromoglutaronitrile is prohibited in leave-on products because of the risk of skin irritation.
Since 2005, "leave-on" products containing methyldibromoglutaronitrile
have been banned from sale in the EU.
Preservatives based on methylisothiazolinone (2-methyl-4-isothiazolin-3-
one) (4.4) and methylchloroisothiazolinone (5-chloro-2-methyl-4-isothiazolin-3-one)
(4.5). These compounds are widely used in hand creams, shampoos and
other cosmetic products.
It has been found that methylchloroisothiazolinone and methylisothiazolinone can cause skin irritation in sensitive individuals. In addition, preservatives based on these compounds sometimes act as contact allergens.
Neurotoxicity of these compounds has also been demonstrated. They inhibit the growth
of neuronal processes (axons)
Formaldehyde-donor preservatives. The good compatibility of these substances with most cosmetic compounds and the synergistic effect (enhancement
of properties in combination with other active substances) ensure
their long-standing and successful use in the manufacture of personal
hygiene products. This group includes dimethylol dimethylhydantoin (4.6), sodium hydroxymethylglycinate, diazolidinyl urea, imidazolidinyl urea,
and so on. In cosmetic products they decompose to release formaldehyde.
Formaldehyde has been found to cause lung cancer. In addition, it
damages DNA, can irritate the eyes, upper respiratory tract and mucous membranes, and can cause asthma and headaches. The use of
formaldehyde-donor preservatives is banned in Japan and Sweden.
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Paraben-based preservatives. Parabens (esters of 4-
hydroxybenzoic acid) are used as preservatives in thousands
of cosmetic products
It has been shown that they can accumulate in oncological tumors
in humans. That is, there is a high probability that they induce their formation.
Parabens act similarly to female sex hormones. They are able to
bind to estrogen receptors (having a hormonal effect on the
female reproductive system).
The estrogenic activity of parabens increases with the size of the
alkyl chain and its branching, in the order methyl < ethyl < propyl <
butyl < isobutyl. However, it should be noted that it is significantly lower than the estrogenic activity of 17-estradiol. Propylparaben (4.7) has a negative effect on the reproductive function of the male body.
Triclosan was first synthesized in Switzerland in 1965. Triclosan (4.8) – a broad-spectrum antibacterial agent, also possessing
anti-inflammatory properties.
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Direct sunlight converts triclosan into one of the forms of dioxin, which is capable of accumulating in the body. Triclosan has been found in 58% of
natural bodies of water in the territory of the United States.
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