Allergic Contact Dermatitis: Epoxy Resins

Allergic contact dermatitis (ACD) is a Type IV hypersensitivity reaction that results from cutaneous exposure to a hapten to which an individual has been sensitized. It can occur in anyone and at any age. Common allergens include nickel; preservatives in cosmetic products, such as methylisothiazolinone and formaldehyde; fragrances and other plants; acrylates; rubber accelerators; certain surfactants in soaps; and paraphenylenediamine in hair dye. In this article, we highlight epoxy resins—a family of chemicals that are combined with a hardener or other curing agent and a reactive diluent to form an epoxy resin system (ERS).

Epoxy resins have strong adhesive properties and are frequently used in 2-part glues and adhesives, as well as protective surface coatings. Uncured epoxy resins are quite sensitizing; however, once cured or hardened, the ERS is inert and nonallergenic. ACD is typically due to the epoxy resin in the ERS, but reactions to hardeners or reactive diluents, although rare, have been reported and should be considered.

Sources of Epoxy Resins

Epoxy resins were first introduced in 1946, and the first cases of epoxy-associated ACD were reported in the 1950s. World production of epoxy resins is around 1 million tons per year.5 Potential sources of epoxy resins include paints; insulation, including electrical insulation; laminates; floor coverings; moldings; primers for cars; steel pipes and other metals; bonding glues; polyvinyl chloride (PVC) production; wood adhesives; and surface coatings on rubber, glass, or ceramics. They are also used in products such as circuit boards, filling agents, printing inks, and immersion oil for microscopes.

In a study of the North American Contact Dermatitis Group database, 5.6% (250 of 4471) of patients with occupational skin disease had a positive reaction to epoxy resins based on diglycidyl ether of bisphenol A (DGEBA). Of these positive reactions, 83.9% (250 of 298) were attributed to an occupational source.11 Occupations associated with ACD from epoxy chemicals include electrical manufacturers, aircraft manufacturers, industrial painters, boat builders, mechanics, plumbers, flooring specialists, and construction workers.

The distribution of ACD from epoxy resins typically involves the hands and upper extremities due to the direct handling of the epoxy chemicals. Airborne exposure to epoxy can also result in ACD of the face, eyelids, and neck. In some cases of airborne epoxy exposure, the hardeners and reactive diluents are the more likely sources because they are more volatile than the epoxy components of the ERS.

Top Allergens in Epoxy Resin Systems

Any component of an ERS (resin, hardener, reactive diluent) can cause irritation or ACD, and sensitization may happen at any time. However, fully cured or hardened products are inert and should not cause ACD. Nevertheless, even in a cured ERS, uncured remnants can still remain for up to 1 week and particles can be released from sawing, drilling, buffing, or sanding, which could result in a reaction.

DGEBA is the most common sensitizer in epoxy resins. Of 209 patients with occupational contact allergy to epoxy chemicals, 82% of patients were sensitized to DGEBA. Diglycidyl ether of bisphenol F (DGEBF) is another common sensitizer in epoxy resins that can cause ACD. There is a greater than 90% crossreactivity between DGEBA and DGEBF. Among 1972 patients tested for DGEBA and epoxy resins based on DGEBF, 96 (4.9%) reacted to DGEBA and 66 (3.3%) to DGEBF. Of the 96 patients who reacted to DGEBA, 61 (63.5%) also reacted to DGEBF.

Individuals may also develop ACD from the hardeners that help cure the epoxy resin. In one study from the Finnish Institute of Occupational Health, the most common hardener to elicit an allergic reaction was m-Xylylenediamine (MXDA) (4.0%, 22/545), followed by 2,4,6-Tris-(dimethylaminomethyl)phenol (tris-DMP) (1.9%, 13/668), and isophorone diisocyanate (IPDI) (1.9%, 12/642). These findings were consistent with previous studies that identified MXDA, tris-DMP, and IPDI as the 3 most common hardeners to cause ACD.

Reactive diluents help lower the viscosity of the ERS and improve ease of handling. In 2 studies, the most common reactive diluents to cause contact allergy were p-tert-Butylphenyl glycidyl ether, phenyl glycidyl ether, 1,4-Butanediol diglycidyl ether, and 1,6-Hexanediol diglycidyl ether.

Additionally, concomitant sensitization is common between epoxy resins and hardeners. In a study using data from the Information Network of Departments of Dermatology, about half of patients who reacted to epoxy resins based on DGEBA were also sensitized to a hardener or reactive diluent.

Patch Testing

When epoxy is suspected of causing ACD, all components of the ERS should be tested. Standard series, such as the North American Contact Dermatitis Group Standard Series and the T.R.U.E. Test, include DGEBA but no hardeners or reactive diluents. Thus, patch testing with supplemental screening series, which should include both hardeners and reactive diluents, is important. Patch testing to the patient’s own resins (diluted) can be carefully attempted and may also be helpful for diagnosis.

Treatment and Management

Adequate training of workers on chemical safety to increase risk awareness is important for prevention of sensitization. For those who are already sensitized, avoidance is key but can be difficult when epoxy resins are a part of a patient’s occupation. Recommendations for avoidance include wearing PVC (vinyl) gloves because rubber or nitrile gloves may not be as protective in the presence of solvents. Similarly, leather and cloth gloves are not suitable for protection. PVC gloves should be multilayered and long-sleeved. The outer layer PVC glove should be removed every 30 to 60 minutes. Once the long-sleeved glove is contaminated, it should also be discarded. It is recommended to mix resins above shoulder level to prevent seepage into the gloves. Patients should try to prevent surface and clothing exposure to epoxy resins; if they do become contaminated, it is important to avoid skin contact from these sources. Wearing a noncontaminated or disposable facial shield may be helpful to prevent touching the face with contaminated hands or surfaces. Medical therapy involving topical steroids or topical immunomodulators may also be incorporated for symptom management.

References:

1. Marks JG Jr, Elsner P, Deleo V. Epoxy resin. Contact & Occupational Dermatology. 3rd ed. Mosby; 2002: 84-87.
2. Bangsgaard N, Thyssen JP, Menné T, et al. Contact allergy to epoxy resin: risk occupations and consequences. Contact Dermatitis. 2012;67(2):73-77. doi:10.1111/j.1600-0536.2012.02072.x
3. Aalto-Korte K, Kuuliala O, Henriks-Eckerman ML, Suuronen K. Contact allergy to reactive diluents and related aliphatic epoxy resins. Contact Dermatitis. 2015;72(6):387-397. doi:10.1111/cod.12369
4. Calnan CD. Studies in contact dermatitis. Trans St Johns Hosp Dermatol Soc. 1958;40:12-19.
5. Cao LY, Sood A, Taylor JS. Hand/face/neck localized pattern: sticky problems— resins. Dermatol Clin. 2009;27(3):227-249. doi:10.1016/j.det.2009.05.012
6. Bjorkner B PA, Zimerson E, et al. Plastic materials. In: Frosch PJ, Menne T, Lepoittevin JP, eds. Contact Dermatitis. 4th ed. Springer; 2006: 583-621.
7. Dickel H, Kuss O, Schmidt A, Diepgen TL. Occupational relevance of positive standard patch-test results in employed persons with an initial report of an occupational skin disease. Int Arch Occup Environ Health. 2002;75(6):423-434. doi:10.1007/s00420-002-0328-2
8. Flyvholm MA. Contact allergens in registered chemical products. Contact Dermatitis. 1991;25(1):49-56. doi:10.1111/j.1600-0536.1991.tb01773.x
9. Taylor JS. Occupational dermatoses. In: Alderman MH, Hanley, MJ, eds. Clinical Medicine for the Occupational Physician. Marcel Dekker, Inc; 1982: 299-344.
10. Hughes R, Taylor JS. Surveillance of allergic contact dermatitis: epoxy resin and microscopic immersion oil. J Am Acad Dermatol. 2002;47(6):965-966. doi:10.1067/mjd.2002.121348
11. DeKoven JG, DeKoven BM, Warshaw EM, et al. Occupational contact dermatitis: retrospective analysis of North American Contact Dermatitis Group data, 2001 to 2016. J Am Acad Dermatol. 2021;86(4):782-790. doi:10.1016/j. jaad.2021.03.042
12. Aalto-Korte K, Pesonen M, Suuronen K. Occupational allergic contact dermatitis caused by epoxy chemicals: occupations, sensitizing products, and diagnosis. Contact Dermatitis. 2015;73(6):336-342. doi:10.1111/cod.12445
13. Canelas MM, Gonçalo M, Figueiredo A. Contact allergy to epoxy resins— a 10-year study. Contact Dermatitis. 2010;62(1):55. doi:10.1111/j.1600- 0536.2009.01652.x
14. Larese Filon F, Delneri A, Rui F, Bovenzi M, Mauro M. Contact dermatitis in northeast Italy mechanics (1996–2016). Dermatitis. 2019;30(2):150-154. doi:10.1097/DER.0000000000000456
15. Dahlquist I, Fregert S. Allergic contact dermatitis from volatile epoxy hardeners and reactive diluents. Contact Dermatitis. 1979;5(6):406-407. doi:10.1111/j.1600-0536.1979.tb04920.x
16. Nixon R, Cahill J, Jolanki R. Epoxy resins. In: Rustemeyer T, Elsner P, John SM, Maibach HI, eds. Kanerva’s Occupational Dermatology. 2nd ed. Springer; 2012: 559-581.
17. Pham HQ, Marks MJ. Epoxy resins. Ullmann’s Encyclopedia of Industrial Chemistry. John Wiley & Sons; 2005.
18. Lee HN, Pokorny CD, Law S, Pratt M, Sasseville D, Storrs FJ. Cross-reactivity among epoxy acrylates and bisphenol F epoxy resins in patients with bisphenol a epoxy resin sensitivity. Am J Contact Dermat. 2002;13(3):108-115.
19. Aalto-Korte K, Suuronen K, Kuuliala O, Henriks-Eckerman ML, Jolanki R. Screening occupational contact allergy to bisphenol F epoxy resin. Contact Dermatitis. 2014;71(3):138-144. doi:10.1111/cod.12223
20. Aalto-Korte K, Suuronen K, Kuuliala O, Henriks-Eckerman ML, Jolanki R. Contact allergy to epoxy hardeners. Contact Dermatitis. 2014;71(3):145-153. doi:10.1111/cod.12280
21. Geier J, Lessmann H, Hillen U, et al. An attempt to improve diagnostics of contact allergy due to epoxy resin systems. First results of the multicentre study EPOX 2002. Contact Dermatitis. 2004;51(5-6):263-272. doi:10.1111/j.0105- 1873.2004.00465.x
22. Rømyhr O, Nyfors A, Leira HL, Smedbold HT. Allergic contact dermatitis caused by epoxy resin systems in industrial painters. Contact Dermatitis. 2006;55(3):167-172. doi:10.1111/j.1600-0536.2006.00894.x
23. Chu CY, Pontén A, Sun CC, Jee SH. Concomitant contact allergy to the resins, reactive diluents and hardener of a bisphenol A/F-based epoxy resin in subway construction workers. Contact Dermatitis. 2006;54(3):131-9.
24. Geier J, Lessmann H, Hillen U, Skudlik C, Jappe U. Sensitization to reactive diluents and hardeners in epoxy resin systems. IVDK data 2002–2011. Part I: reaction frequencies. Contact Dermatitis. 2016;74(2):83-93. doi:10.1111/cod.12491
25. Suuronen K, Bäck B, Aalto-Korte K, et al. Skin exposure to epoxy chemicals in construction coating, assessed by observation, interviews, and measurements. Contact Dermatitis. 2019;80(1):18-25. doi:10.1111/cod.13122