We use a wide variety of different cosmetic products every day. These may inadvertently contain or be contaminated with substances in various ways, but not every substance compromises the safety and tolerability of cosme-tic products. As part of the safety assessment of a cosmetic product, consideration is given to the toxicological relevance of a substance and whether it may have a harmful effect on the consumer.
Pursuant to Articles 14 and 15 of Regulation (EC) No. 1223/2009, the substances listed in Annex II are prohibited in cosmetic products. The presence of small amounts (in the ppm or ppb range) of these prohibited substances cannot always be prevented and is defined by law as an impurity. According to Article 17 of Regulation (EC) No. 1223/2009, the presence of such substances in cosmetics is permitted only if they are technically unavoidable under good manufacturing practices and do not compromise the safety of the cosmetic product.
As part of the safety assessment conducted in accordance with Article 10, information regarding the purity of the substances or mixtures used must be provided, and evidence must be presented to demonstrate that the impurities are technically unavoidable. Impurities are not intentionally added to the product and are therefore, in legal terms, not considered to be ingredients and do not need to be labeled.[1]
Where do impurities or undesirable substances come from?
The sources of impurities can be very diverse. The origin of the raw material plays a decisive role here. For example, plant-based raw materials such as herbs, fats/oils, and plant parts may contain pesticide residues. Furocoumarins can enter cosmetic products, for example, from the peel of citrus fruits. Furocoumarins are phototoxic and must be treated with caution in cosmetics that are exposed to sunlight. In mineral raw materials, for example, heavy metals may be present as impurities. Thus, the selection of raw materials is a critical aspect of manufacturing and must be ensured through raw material certificates and batch testing/inspections in accordance with GMP.
The manufacturing process is another major source of impurities. Undesirable byproducts can form during this process. For example, 1,4-dioxane can be formed as a byproduct during the production of the surfactant sodium laureth sulfate. This substance can be found in corresponding shampoo and toothpaste formulations and is suspected of being carcinogenic.[2] Residual solvents, catalysts, and reactants can also lead to impurities. During the synthesis of the preservative phenoxyethanol, residues of phenol, which is used as the starting compound, may remain in the product.
The formulation of cosmetic products must be designed so that no prohibited substances are formed because of reactions between the raw materials used. For example, nitrosamines can be formed through the combination of nitrites and secondary amine compounds.[3]
This can also occur, for example, upon contact with the primary packaging. Migration processes can lead to the unintentional transfer of substances from the packaging material. Various phthalates are frequently used as plasticizers in plastic packaging.
The presence of some of these phthalates, such as diethylhexyl phthalate (DEHP), dibutyl phthalate (DBP), and benzyl butyl phthalate (BBP), is prohibited in cosmetic products under Annex II of Regulation (EC) No. 1223/2009, as they are classified as endocrine disruptors.[1][4] According to the assessment by the Scientific Committee on Consumer Safety (SCCS), concentrations of up to 100 mg/kg for these three substances pose no health risk.[5]
The choice of packaging material must be adapted to the nature of the cosmetic product in such a way that no undesirable migration of substances occurs. Therefore, when selecting packaging, care must be taken to ensure that all primary packaging components meet the required standards.
In addition to chemical contamination, cosmetic products can also become contaminated with microorganisms. This can occur through contaminated raw materials, poor workplace hygiene, inadequate preservation, and, of course, through the product’s users.
How are contaminants assessed?
Some contaminants are regulated by specific limit values. For other contaminants, there are only guideline values and/or reference values. Since new products with new raw materials, manufacturing processes, and packaging are constantly being introduced, these guideline values may also change.[3]
Guideline values are usually determined as part of a monitoring program and are intended to reflect as many comparable products as possible regarding the substance in question. The 90% percentile is calculated from the results, which represents a large portion, but not all, of the product categories. Levels in cosmetic products above this value are considered technically avoidable, but unlike limit values, guideline values are not legally binding.[3]
One example of such monitoring is the testing of heavy metal levels in cosmetic products:
Heavy metals are common contaminants in mineral raw materials. Mineral raw materials are frequently used as colorants or pigments. Powder and cream products, face masks, decorative cosmetics, and toothpaste are particularly affected. Based on monitoring data, the Federal Office for Consumer Protection and Food Safety (BVL) has established guideline values for the unavoidable presence of lead, cadmium, mercury, arsenic, and antimony under good manufacturing practices.[6] Only a very small proportion of these heavy metals, usually less than 1%, is absorbed through the skin. For the analytical digestion of the heavy metals as part of the monitoring process, extreme analytical conditions (temperature, acids, microwave radiation, pressure) are required to break down the lattice structure of the heavy metals. Under normal cosmetic use, these conditions are not reached, so the heavy metals are not bioavailable. This reduces the risk of absorption through the skin.
Heavy metals are ubiquitous in the environment. Absorption through food and drinking water is more significant than that through cosmetics.[7]
One example of a legal regulation concerns impurities in UV filters:
Diethylamino-hydroxybenzoyl-hexylbenzoate (DHHB) is used as a UV filter in many sunscreen products. Analyses have detected di-n-hexyl phthalate (DnHexP) in some of these sunscreens. DnHexP is classified as toxic to reproduction and is therefore banned in cosmetic products.[1] Because it is formed as a byproduct during the synthesis of DHHB, it can enter sunscreens as an unintended impurity. It is absorbed through the skin. In the body, it is metabolized via the cleavage of an ester bond to form mono-n-hexyl phthalate (MnHexP). From this, further oxofunctionalized metabolites can be formed. As part of a human biomonitoring study, MnHexP was detected in urine samples from children.[8]
Because DnHexP is produced as a byproduct of DHHB synthesis, the degree of contamination in raw materials varies depending on the manufacturer and manufacturing process. Sunscreen manufacturers have acted, resulting in a significant reduction in the number of sunscreens in which DnHexP has been detected. The DnHexP content in sunscreens has also decreased. DHHB manufacturers have also acted, making raw materials with a DnHexP content below 10 mg/kg available on the market.[9]
At the EU level, the SCCS has evaluated DnHexP. According to its assessment, DHHB may contain no more than 260 mg/kg of DnHexP to ensure that its use in cosmetic products does not pose a health risk. In addition, the SCCS is aiming for a maximum concentration of 1 mg/kg of DnHexP in DHHP.[10] According to manufacturers, this would lead to a sharp increase in production costs. As a compromise, the European Commission has decided that, starting in January 2027, a limit of 10 mg/kg of DnHexP in DHHP will apply. Thanks to a transition period, products that do not meet this requirement may still be sold until July 2028.[11]
In summary, contaminants in cosmetic products can originate from raw materials, manufacturing processes, packaging, or microbial sources, and are legally permissible only when they are technically unavoidable under GMP and do not compromise product safety. Each impurity must be evaluated separately; decisions are made on a case-by-case basis, always with the goal of ensuring the highest level of consumer safety.
References:
1 Regulation (EC) No 1223/2009 of the European Parliament and of the Councile of 30 November 2009 on cosmetic products.
2 National Toxicology Program, Department of Health and Human Services, 15th Report on Carcinogens 1,4-Dioxane, 202; RoC Profile: 1,4-Dioxane; 15th RoC 2021.
3 Keck-Wilhelm, A., Kratz, E., Baumung, C., Gutsche, B., Schneider, B., Mildau, G. (2017), Verbotene Stoffe in kosmetischen Mitteln.
4 German Federal Institute for Risk Assessment (BfR) (2024), Fragen und Antworten zu Phthalat-Weichmachern. Fragen und Antworten zu Phthalat-Weichmachern – BfR.
5 Scientific Committee on Consumer Safety (SCCS) (2007), Opinion on phthalates in cosmetic products, Microsoft Word – opinion on phthalates 21 mar 07_corr.doc.
6 Federal Office of Consumer Protection and Food Safety (BVL) (2017), Technically avoidable heavy metal contents in cosmetic products, J Consum Prot Food Saf; 12: 51-53; DOI 10.1007/s00003-016-1044-2.
7 German Federal Institute for Risk Assessment (BfR) (2006), Kosmetische Mittel: Schwermetalle. Kosmetische Mittel: BfR empfiehlt Schwermetallgehalte über Reinheitsanforderungen der Ausgangsstoffe zu regeln.
8 German Federal Institute for Risk Assessment (BfR) (2024), MnHexP in Urinproben: Bewertung des gesundheitlichen Risikos, MnHexP in Urinproben: Bewertung des gesundheitlichen Risikos.
9 Chemical and Veterinary Investigation Office (CVUA) Karlsruhe (2026), Weichmacher DnHexP in Sonnenschutzmittel – nur noch wenige Produkte sind auffällig, CVUA Karlsruhe | Weichmacher DnHexP in Son….
10 Scientific Committee on Consumer Safety (SCCS) (2025), Scientific Advice on the safety of Diethylamino Hydroxybenzoyl Hexyl Benzoate – DHHB – S83, SCCS – Scientific Advice on the safety of Diethylamino Hydroxybenzoyl Hexyl Benzoate – DHHB – S83 – Public Health.
11 Commission Regulation (EU) 2026/909 of 27 April 2026 amending Regulation (EC) No 1223/2009 of the European Parliament and of the Council as regards the use of DHHB in cosmetic products.
Anton Szcepaniak
Food Chemist, Lemikos, Wiehl,
www.lemikos.de