Zinc Pyrithione

Figure 1. Shampoo containing zinc pyrithione is not allowed in Europe.

Figure 2. Chemical structure of zinc pyrithione.

Zinc pyrithione is a fine beige powder that is antibacterial, antifungal, and antimicrobial.2,3 It is mainly used to treat seborrheic dermatitis (dandruff)1,11, scalp psoriasis3,11, ring worm11 and athlete's foot.11 Another interesting use for zinc pyrithione is that it is used as a biocide for product preservation by preventing fouling. Some items include films, fibres, leather, rubber, polymers and construction materials.4,12 Zinc pyrithione can only be obtained through synthesis in a lab.10 Production includes three simple addition steps of aqueous solutions.10 Please refer to source 10 which is the patent for production, it includes the steps in detail if you are interested.

The European Union as of March 1, 2022, classified zinc pyrithione as a 1B CMR. A CMR is any substance that is carcinogenic, mutagenic or a reproductive toxin, while the 1B classifier means that this was verified through animal studies.5,6 Zinc pyrithione is not the most toxic substance out there but it can be pretty toxic in industrial concentrations. Its dermal LD50 is about 100mg/kg in rabbits.2 The LD50 of a substance is the lethal dose that it takes to kill half the population. Orally its LD50 is 177mg/kg for rats, 160mg/kg for mice and 600mg/kg for dogs.2,7 Inhaling zinc pyrithione is much more deadly with an LD50 of 140 ppm.2,7

The FDA limits how much zinc pyrithione is allowed in the products that we buy. They limit the percentage to 0.1-0.25% if the product is a apply and leave-on product. While the percentage for products that are applied and rinsed off must contain no more than 0.3-2% zinc pyrithione.13 

Some alternatives to zinc pyrithione include piroctone olamine8 and selenium sulphide9 being the most similar. Other options include Ketoconazole, coal tar, coconut oil, apple cider vinegar, essential tea tree oil and raw honey.3 The latter options are less effective in comparison to the before-mentioned synthesized options.

References:

[1] Pyrithione, 2010. DrugBank. https://go.drugbank.com/drugs/DB06815 (accessed February 7, 2023).

[2] Zinc pyrithione (T3D0740), 2014. Toxin and Toxin Target Database (T3DB).

http://www.t3db.ca/toxins/T3D0740 (accessed February 7, 2023).

[3] Gallagher, G. How Pyrithione Zinc Is Used in Skin Care.

  https://www.healthline.com/health/pyrithione-zinc#side-effects (accessed February 7, 2023).

            Healthline.

[4] Substance Infocard, Pyrithione zinc, 2022. European chemical agency (ECHA).

https://echa.europa.eu/substance-information/-/substanceinfo/100.033.324 (accessed February

7, 2023). An agency of the European Union.

[5] Santacatterina, F. Lilial and Zinc pyrithione banned in the EU, 2022. Obelis Group.

            https://www.obelis.net/news/lilial-and-zinc-pyrithione-banned-in-the-

            eu/#:~:text=The%20European%20Commission%20has%20prohibited,reproduction%20based

            %20on%20animal%20studies. (accessed February 7, 2023).

[6] Pro, L. CMR Category 1A/1B Substances, 2017. ChemSafetyPRO.

https://www.chemsafetypro.com/Topics/Restriction/REACH_annex_xvii_restriction_CMR_subst

ance_1A_1B.html (accessed February 7, 2023).

[7] OPINION ON Zinc Pyrithione (ZPT) (P81); CAS No. 13463-41-7 [Online]; Scientific Committees on

            Consumer Safety. https://health.ec.europa.eu/system/files/2021-11/sccs_o_236.pdf (accessed

            February 7, 2023). European Commission.

[8] Piroctone olamine. https://en.wikipedia.org/wiki/Piroctone_olamine (accessed February 7, 2023).

            Wikipedia.

[9] Selenium disulfide. https://en.wikipedia.org/wiki/Selenium_disulfide (accessed February 7, 2023).

            Wikipedia.

[10] Douglas A. Farmer; Jr., Madison; Lawrence E. Katz. PROCESS FOR PRODUCING SODUMAND

            ZINC PYRTHIONE. Patent 4,396,766, Apr 28, 1982.  

[11] Molecule of the Week Archive, Zinc pyrithione, 2014. American Chemical Society (ACS).

  https://www.acs.org/molecule-of-the-week/archive/z/zinc-pyrithione.html (accessed February 7,

            2023).

[12] Soon, Z. Y., Jung, J.-H., Jang, M., Kang, J.-H., Jang, M.-C., Lee, J.-S., & Kim, M. (2019). Zinc

            Pyrithione (ZnPT) as an Antifouling Biocide in the Marine Environment—a Literature Review of

            Its Toxicity, Environmental Fates, and Analytical Methods. Water, Air, and Soil Pollution,

            230(12). https://doi.org/10.1007/s11270-019-4361-0

[13] Code of Federal Regulations Title 21, 1994. US Drug & Food Administration.

            https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=358.710#:~:text=

            (3)%20Pyrithione%20zinc%2C%200.1,acid%2C%201.8%20to%203%20percent.  (accessed

            February 7, 2023). Title 21, Volume 5, No. 21CFR358.710.

Figure 1. Shampoo containing zinc pyrithione is not allowed in Europe. 

Source 1: European map clipart, pink illustration.

https://www.rawpixel.com/image/6481398/image-public-domain-pink-illustrations (accessed

February 7, 2023). Rawpixel. Free public domain CC0 image.

Source 2: Head & Shoulders shampoo bottle, WikiMedia Commons.

https://commons.wikimedia.org/wiki/File:Head_%26_Shoulders_shampoo_bottle.jpg (accessed

February 7, 2023). WikiMedia Commons. (CC BY-SA 3.0)

Figure 2. Chemical structure of zinc pyrithione. 

Source: PubChem.  Zinc pyrithione.

https://www.whatsinproducts.com/chemicals/view/1/971/013463-41-7/Zinc%20pyrithione

(accessed February 7, 2023). Reprinted with permission.