October 14, 2024
2-Hydroxyethyl Methacrylate (HEMA) is a UV-curable monomer that, through a polymerization reaction initiated by the breakdown of photoinitiators under UV/LED light, transforms into long polymer chains, creating a product with high durability and excellent strength. Due to the presence of a polymerizable methacrylate group at one end of its molecule and a reactive hydroxyl group at the other, HEMA easily copolymerizes with a wide range of polymers and exhibits strong hydrophilic properties, responsible for its excellent water absorption and adhesion to the surface of the final product [1]
Due to its excellent properties, HEMA is used in the synthesis of products that require high durability, mechanical strength, and excellent adhesion. This includes nail styling products such as hybrid polishes and gels, where HEMA plays a key role in ensuring the proper consistency of formulations, making the product easy to apply. Additionally, it acts as a binding agent, ensuring the polish adheres well to the nail plate, providing durability and resistance to chipping. This distinguishes it from products that do not contain HEMA, which may be prone to faster peeling or chipping [2].
However, the use of this compound is not limited to the cosmetics industry. HEMA is also a key component in specialized coatings, adhesives, printing inks, and acrylic materials [3]. Additionally, HEMA belongs to the group of hydrogels, which are hydrophilic polymer materials capable of absorbing large amounts of water while maintaining a three-dimensional network structure. They resemble natural tissues and are thus highly biocompatible and biologically inert. Due to these properties, they are widely used in the biomedical and pharmaceutical industries for the production of contact lenses, biosensors, membranes, artificial organs, and controlled drug delivery systems [4]. Furthermore, HEMA plays a crucial role in dentistry, where, alongside methyl methacrylate, it is one of the most commonly used acrylate monomers in the production of dental fillings [5].
As can be seen, HEMA is a very important substrate today, making it difficult to imagine the modern chemical industry without it. However, in recent years, it has garnered some negative attention in nail styling products due to reports of potential allergic reactions. In 2018, the European Commission's Scientific Committee on Consumer Safety (SCCS) issued an opinion on the safety of HEMA. The SCCS determined that the maximum safe concentration of HEMA in nail styling products is up to 35%. The report also stated that HEMA is a weak to moderate sensitizer and poses a risk of sensitization only when products are improperly used, applied incorrectly, or accidentally contaminate the skin around the nails under normal and reasonably foreseeable conditions of use. Additionally, the data showed that the normal nail plate acts as a good barrier to chemical penetration, and since 2-hydroxyethyl methacrylate polymerizes quickly under UV curing, there is very little chance of monomers being absorbed through the nail plate in any significant amount [6].
Cured acrylic resin products typically do not cause allergic reactions or symptoms in previously sensitized individuals, as they do not contain enough reactive monomers. However, especially when curing is incomplete (e.g., due to improper curing techniques), residual monomers may remain in the final product, which over time can cause contact allergy or allergic contact dermatitis (ACD) [7]. Therefore, it is recommended that such products be used only by professionals.
In the interest of consumer health, in November 2020, the EU Commission issued Regulation 2020/1682, amending Annex III of Regulation (EC) No 1223/2009 concerning cosmetic products, allowing only professional use of nail products containing HEMA. Warnings such as "for professional use only" and "may cause an allergic reaction" must be placed on the packaging of any such preparation. Manufacturers are required to appropriately label their products and ensure that the HEMA content does not exceed the permitted limit [8].
2-Hydroxyethyl methacrylate is a compound commonly used in many industries, especially in the cosmetics sector. Its curing and aesthetic properties make it extremely popular in nail products. However, it is essential to also consider the potential allergic risks and associated regulations. It is crucial for all consumers to make informed decisions, allowing them to safely use cosmetic products and enjoy their benefits while minimizing potential health risks.
[1] A. Kimya. “2-HYDROXYETHYL METHACRYLATE (HEMA)” - Accessed: Oct. 03, 2024. [Online]. Available: https://www.atamanchemicals.com/2-hydroxyethyl-methacrylate-hema_u30350/
[2] “The Role of HEMA in the Nail Industry - NailKnowledge.” Accessed: Oct. 03, 2024. [Online]. Available: https://nailknowledge.org/blog/the-role-of-hema-in-the-nail-industry
[3] K. Kema Ajekwene, “Properties and Applications of Acrylates,” Acrylate Polymers for Advanced Applications, May 2020
[4] L. Li and L. J. Lee, “Photopolymerization of HEMA/DEGDMA hydrogels in solution,” Polymer (Guildf), vol. 46, no. 25, pp. 11540–11547, Nov. 2005
[5] S. Alizadehgharib, A. K. Östberg, and U. Dahlgren, “Effects of the methacrylate/acrylate monomers HEMA, TEGDMA, DEGDA, and EMA on the immune system,” Clin Exp Dent Res, vol. 3, no. 6, pp. 227–234, Dec. 2017
[6] “Opinion on the safety of cosmetic ingredients HEMA and Di-HEMA Trimethylhexyl Dicarbamate - Publications Office of the EU.” Accessed: Oct. 03, 2024. [Online]. Available: https://op.europa.eu/pl/publication-detail/-/publication/b9e91eef-38cb-11e9-8d04-01aa75ed71a1
[7] A. C. de Groot and T. Rustemeyer, “2-Hydroxyethyl methacrylate (HEMA): A clinical review of contact allergy and allergic contact dermatitis—Part 1. Introduction, epidemiology, case series and case reports,” Contact Dermatitis, vol. 89, no. 6, pp. 401–433
[8] REGULATION (EU) 2020/1682 of the Commission of November 12, 2020, amending Annex III to Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products
