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Question 1, What are cosmetic preservatives?

Cosmetic preservatives are a kind of raw material widely used in cosmetics. According to the “Cosmetics Safety Technical Specifications”, preservatives refer to substances added to cosmetics for the purpose of inhibiting the growth of microorganisms in cosmetics. Since most cosmetics contain moisture and nutrients suitable for microbial growth, corruption and deterioration of transactions will not only damage the appearance of cosmetics, but also bring certain health risks to users. Therefore, it is generally necessary to add appropriate preservatives to ensure the quality and safety of the product during use and storage. In cosmetic formulations, whether the construction of the anti-corrosion system is reasonable and whether it can exert the expected anti-corrosion effect is an important indicator.

Qutstion 2, What is the role of preservatives in cosmetics?

Microorganisms are ubiquitous in our lives, and many raw materials in cosmetics are nutrients for the growth and reproduction of microorganisms. In order to avoid the corruption of cosmetics during production, storage and use, it is generally necessary to add antiseptic agents to inhibit the growth of microorganisms to ensure It will not deteriorate due to the growth of microorganisms during use.

The main purpose is to prevent the growth of microorganisms, reasonably extend the shelf life of the product, and ensure that the product will not deteriorate due to various contamination during use. Preservative skin care products and maintenance ingredients in skin care products are mostly natural organic substances such as amino acids, proteins, sugars, vitamins, vegetable gums, etc., which are good environments for bacteria and microorganisms to breed. Therefore, preservatives are common ingredients in the manufacturing process of skin care products. In theory, under the premise of the same efficacy, the lower the dose of added preservatives, the lower the probability of allergy.

Question 3, What are the common cosmetic preservatives?

Preservatives usually inhibit and kill microorganisms by acting on the cells of microorganisms. Since they can act on microbial cells, they can also have a certain effect on human cells . Dosage is specified .

Today, let’s get to know the preservatives and bacteriostatic agents commonly used in cosmetics!

  1. Alcohol bacteriostatic agents and bacteriostatic synergists

mechanism of action

lower alcohols have bacteriostatic or assisting bacteriostatic effects, but their bacteriostatic abilities are quite different . Studies have shown that certain glycols have been shown to have better bacteriostatic or assist in bacteriostatic effects, including pentanediol, hexylene glycol, caprylyl glycol (caprylyl glycol), decanediol, etc.; while certain alcohols The effect of single use is not ideal, and it is suitable for synergy with other types of bacteriostatic agents.

High concentrations of alcohols can destroy the integrity of cell membranes, allowing cell contents to leak out and act on microorganisms quickly; low concentrations of alcohols can change the permeability of cell membranes. Most alcohols require high concentrations to be bacteriostatic, and are suitable as synergists for other bacteriostatic agents at low concentrations.

In addition to inhibiting cell activity by itself, alcohols can form unstable alcohol complexes with other types of bacteriostatic agents due to the presence of hydroxyl groups, and enter the cell body through the cell membrane through the affinity of hydroxyl groups with cell membranes, which significantly improves other Bacteriostatic effect of bacteriostatic agents.

After destroying the permeability of the cell membrane, some alcohols can also reduce the activity of enzymes, inhibit the synthesis of DNA, and form secondary effects.

Common bacteriostatic agents and bacteriostatic synergists

In general, alcohol antibacterial synergists are safe, non-sensitizing to the skin, relatively stable, and can be used in combination with most antibacterial agents, and it is difficult for microorganisms to form resistance to them. The disadvantage is that the added amount is slightly higher than that of traditional bacteriostatic agents.

(1) Phenoxyethanol (this antibacterial agent is a common preservative in cosmetics)

Phenoxyethanol preservative is slightly irritating to the skin and will not cause damage. 0.5-1.0% has better antibacterial effect, especially on Pseudomonas aeruginosa. Concentrations above 0.3% have a strong heat sensation in the mask. Suitable for use with antibacterial synergists.

  • The following are bacteriostatic synergists:

(2) Ethanol

It is widely used in perfumes, and the 75% volume concentration has the best bactericidal effect. As a bacteriostatic agent, the concentration is generally greater than 15%, and less than 15% can be used as a bacteriostatic synergist.

(3) Propylene glycol, butylene glycol

In the current formulation system, the bacteriostatic effect is very weak. But when used in combination with other bacteriostatic agents, it has the effect of bacteriostatic and synergistic effect. Sweet taste, less irritating to mucous membranes.

(4) Benzyl alcohol, phenethyl alcohol

It is flammable, toxic, dangerous, and irritating. Harmful to the body after inhalation, ingestion or absorption through the skin, children’s products should be used with caution.

(5) Diols

Originally used as a moisturizer and to enhance the skin feel of cosmetics, it is not listed on the list of preservatives to be restricted.

Diols have a better synergistic effect, because the position of the hydroxyl group is different, the bacteriostatic effect is very different. When located at one end, the glycol substance is more likely to penetrate into the cell body through the cell membrane.

With the growth of the carbon chain, the 1 and 2 diols have enhanced bacteriostatic ability, increased irritation, increased melting point, and decreased water solubility. Bacteriostatic ability: 1,2-decanediol>octane glycol>1,2-hexanediol>1,2pentanediol. (The heat sensation of caprylyl glycol is obvious when the dosage is more than 0.2%)

(6) Ethylhexylglycerin

Ethylhexylglycerol is generally used in combination with phenoxyethanol, and the usual amount is 1∕9 of phenoxyethanol.

 laws and regulations

  1. China, the European Union, Japan, and the United States stipulate that the maximum concentration of phenoxyethanol is 1% .
  2. Countries have no restrictions on the use of glycols as antibacterial synergists .
  3. Halogen antibacterial agents

mechanism of action

Common halogen bacteriostatic agents mainly include IPBC (iodopropynyl butyl carbamate) and 2-bromo-2-nitro-1,3-propanediol. They do not have the same antibacterial mechanism as other categories. For example, IPBC can slowly release iodide ions in the system, which is toxic to microorganisms. Very low doses of iodide ions can also have a strong poisoning effect on molds.

Infants under the age of 3 should not use IPBC preservatives, and it is prohibited to use in lip products and body skin care products (such as body creams).

Three, isothiazolinone antibacterial agents

mechanism of action

In cosmetics, commonly used isothiazolinone bacteriostatic agents are generally composed of two monomers: CIT (methylchloroisothiazolinone) and MIT (methylisothiazolinone) . These bacteriostatic agents can change the permeability of the cell membrane, resulting in the leakage of part of the cell contents, but do not destroy the integrity of the cell membrane; at the same time, it reacts with the intracellular sulfhydryl enzymes to form disulfides, resulting in the inactivation of sulfhydryl-containing enzymes. , resulting in bacterial metabolic disorders until death.

CIT can continue to react to form thioacyl chloride on the basis of forming disulfide. Thioacyl chloride has extremely high intracellular activity and can interact with macromolecules in cells, resulting in cell inactivation. Therefore, CIT has high activity and can kill microorganisms in a short time, but CIT is extremely unstable and is easily inactivated by the influence of heat, alkali, reducing and oxidizing substances.

MIT is stable in nature and has a wider pH range (2-12), but it has poor inhibitory effect on mold, and other bacteriostatic agents are often required. MIT is cumulative and has the potential to cause allergic problems such as dermatitis .

Application status

MIT was previously regarded as a high-efficiency and low-irritant product. It has been widely used in children’s products and resident products since 2009. However, it was confirmed by the European Union Daily Chemicals Association in 2012 that it can cause serious allergies . Evaluate. CIT (Methylchloroisothiazolinone): MIT (Methylisothiazolinone) = 3:1 mixture can be used in non-leave-on cosmetics, the maximum concentration is 15ppm, when only methylisothiazolinone is used The EU also only allows 15 ppm, and when a mixture of CIT and MIT is used, MIT cannot be added.

  1. Formaldehyde sustained-release bacteriostatic agents

mechanism of action

Formaldehyde sustained-release bacteriostatic agents can slowly decompose to generate free formaldehyde. With the continuous release of formaldehyde, after reaching a certain concentration range, formaldehyde sustained-release body and free formaldehyde reach a relative equilibrium state and form an effective bacteriostatic system.

Formaldehyde can penetrate into the interior of the cell through the cell membrane without obstruction, and at the same time, formaldehyde can alkylate the amino, sulfhydryl and purine base nitrogen heterocycles in the protein, denature the protein, and eventually lead to the death of the bacteria. Although this type of preservative releases formaldehyde, it is relatively safe due to its slow release.

Representative ingredients

(1) Bis (hydroxymethyl) imidazolidinyl urea, imidazolidinyl urea

Bisimidazolidinyl urea has high carrying capacity and strong bacteriostatic ability, and is widely used in China; imidazolidinyl urea is more commonly used in Europe.

(2) DMDMH

Also known as DMDM hydantoin, 1,3-dimethylol-5,5-dimethylhydantoin. It is a colorless and transparent liquid with a slight aldehyde smell, which is commonly used in washing products.


  1. Parabens (also known as hydroxybenzoates or parabens)

mechanism of action

Parabens have been used as bacteriostatic agents for nearly 100 years and are widely used. Because of its broad antibacterial spectrum and low skin irritation, it is relatively well recognized in cosmetics. Its mechanism of action is that such molecular structures can enter the microbial cell membrane to change its permeability, resulting in the leakage of intracellular lysates, and at the same time inactivating the ion transfer protein in the cell membrane, resulting in the loss of the energy gradient coupled to it.

representative ingredients

Parabens generally include methyl, ethyl, propyl, butyl and their salts. They are called methylparaben, ethyl, propyl, butyl and their salts in cosmetics. They are widely used, among which methylparaben ( MP) and propylparaben (PP) are typical representatives.

The paraben “preservative crisis” began in 2004 when a scientific paper linked the presence of parabens in humans to breast tumors. The controversial article went viral, and so far, there is no direct evidence that parabens are directly linked to cancer. At effective concentrations, paraben preservatives are considered safe.

Application status

At present, parabens are still widely used in cosmetic companies, and parabens can be found in the ingredient list of most products; however, there are also some high-end skin care brands that have gradually incorporated The formula is upgraded to a system without parabens.

Question 3, Do cosmetic preservatives have side effects?

Common preservatives in shampoos are methylisothiazolinone, methylchloroisothiazolinone, DMDM hydantoin, bisimidazolidinyl urea, sodium benzoate, 

Methylisothiazolinone, methylchloroisothiazolinone are allergenic and both chemical preservatives have been banned in the European Union.

DMDM hydantoin, bisimidazolidinyl urea These urea preservatives preserve by releasing formaldehyde, which is a class of carcinogens.

Sodium benzoate is harmful to the human body. Sodium benzoate will react with gastric acid in the human body to generate benzoic acid. Benzoic acid has certain toxicity, and long-term drinking can cause chronic benzene poisoning in humans. The symptoms of chronic benzene poisoning are mainly neurasthenia, such as headache, dizziness, memory loss, insomnia, fatigue, etc. At the same time, the patient will also have leukopenia, and even severe aplastic anemia.

Compared with the previous concentrated preservatives, phenoxyethanol is relatively less irritating, but it is easy to produce phenol and dioxane during synthesis. Both are carcinogens.

Popular polyols in recent years, such as pentanediol, hexanediol. Because it is not in the list of cosmetic preservatives, many businesses add this ingredient to replace preservatives and claim to be free of preservatives. These ingredients are relatively safer, but they are irritating to the eyes, and a small number of people will be allergic to them.

Plant bacteriostatic agents extracted from plants do not belong to the preservative system. Compared with the above substances, they are the safest antibacterial ingredients in cosmetics. However, because of their high cost and short antiseptic period, most products will not add such ingredients. , will not be discussed here.

Question 4, Which preservatives are safer to use in skin care products

  1. Potassium sorbate. Potassium sorbate is a recognized safe preservative and is often added to foods. When used in skin care products, as the molecules are absorbed by the skin, they are easily degraded and disappear, and will soon be metabolized and excreted from the body, and are widely used.
  2. Plant extracts. Plant extracts are natural preservatives added to skin care products. While ensuring the antiseptic function, it will not add extra burden to the skin. Moreover, the added dose only needs a small amount to meet the antiseptic function, and it is easy to metabolize after being absorbed by the skin.

Question 5. Are preservative-free cosmetics necessarily safer than preservative-containing cosmetics?

In recent years, as consumers pay more and more attention to health and safety, a class of products featuring no preservatives have appeared on the market, some of which are in disposable small packaging. Such products have higher requirements on the production environment and packaging, and some belong to the province. Microorganisms are not easy to grow, such as perfumes containing a lot of ethanol, and substrates that do not contain moisture, such as dry powder, etc. Of course, there are still some that belong to the concept of stealing or misleading publicity, and even use unapproved preservatives. Compared with other products, the safety risk has not decreased but increased. In fact, cosmetic preservatives have a scientific and rigorous management system in China. Scope, etc., as long as it is a product from a formal channel and meets the requirements of regulations, its quality and safety can generally be guaranteed. Consumers should treat the problem of preservatives scientifically and reasonably, make rational choices, and use cosmetics with peace of mind.

Question 6, What characteristics should preservatives in qualified skin care products have?


1. Broad-spectrum activity
2. Low effective concentration
3. Good compatibility with various surfactants
3. Low irritation
4. PH is stable to temperature, 4-4.5 is ideal

 

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