Zinc is a trace mineral and is vital to the human body and all forms of life, having catalytic, structural and regulatory functions. On the other hand, high levels of dietary zinc can cause anemia, decreased levels of copper and iron absorption and reduction of enzyme activities in several tissues. In 2003, the Scientific Committee on Food established a tolerable total uptake level (UL) of Zinc up to 25 mg. [1,2]
In the cosmetic industry, Zinc and zinc salts are used in a variety of categories. Cosmetic products might account for maximum 10% of the UL. One of the most widely used zinc salt is Zinc Pyrithione. It is an aromatic zinc compound used as an antidandruff, antiseborrhoeic, hair conditioning agent and preservative in cosmetics and personal care products. In the European Union (EU), Zinc Pyrithione is included in the Annex III of the European Cosmetic Regulation No. 1223/2009, which means its use is subject to the restrictions laid down. According to this Regulation, Zinc Pyrithione is also included in the Annex V (list of preservatives allowed in cosmetic products), and may be used as a preservative in rinse-off products (excluding oral hygiene products) in a concentration up to 0.5% in general and up to 1.0% in leave-on hair products (Annex V/8). This compound has been used for more than 60 years as an anti-dandruff agent, in concentration up to 1-2%. The U.S. Food and Drug Administration (FDA) allows the use of Zinc Pyrithione as an active ingredient in Over-The-Counter (OTC) dandruff and seborrheic dermatitis drug products.
The European Scientific Committee on Consumer Safety (SCCS) has issued an opinion (March 2020) regarding the safety of Zinc Pyrithione (ZPT) in cosmetic products. The SCCS concluded that Zinc Pyrithione was “safe when used as an anti-dandruff in rinse-off hair products up to a maximum concentration of 1%”. This opinion updated previous SCCS opinions, that stated that this ingredient was safe up to 2% as an antidandruff agent in rinse-off products. [3,4]
In 2018, ECHA’s Risk Assessment Committee (RAC) issued an opinion proposing harmonized classification and labelling at EU level of Zinc Pyrithione as a CMR 1B substance under Regulation (EC) No. 1272/2008 (presumed human carcinogen, mutagen or reproductive toxicant based on animal studies). According to this Regulation, the use of this type of substances shall be prohibited in cosmetic products, unless, by way of exception, specific conditions are fulfilled. 
Zinc Pyrithione was at least a mild skin irritant to human volunteers and it was a severe eye irritant in animal studies. This compound was not a skin sensitizer when tested in guinea pigs and it demonstrated a low potential to induce contact hypersensitivity in humans, when tested alone or in cosmetic formulations. Zinc Pyrithione is neither genotoxic nor mutagenic in vivo and in vitro. It showed no evidence of carcinogenic potential in chronic oral and dermal studies. 
NOTA: Não encontro nem a entrada do Anexo III (III/101) nem do V (V/8) correspondente a este ingrediente. Não percebo o que isso significa.
- Cosing – European Commision database for information on cosmetic substances and ingredients – https://ec.europa.eu/growth/tools-databases/cosing/
- European Food Safety Authority – Re-evaluation of Silicon Dioxide (E 551) as a food additive – https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2018.5088
- U.S. Food and Drug Administration (FDA) – Code of Federal Regulations – https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm?fr=172.480
- Regulation (EC) No 1223/2009 of the European Parliament and of the Council of 30 November 2009 on cosmetic products – https://ec.europa.eu/health/sites/health/files/endocrine_disruptors/docs/cosmetic_1223_2009_regulation_en.pdf
- Scientific Committee on Consumer Safety (SCCS) – Opinion on solubility of Synthetic Amorphous Silica (SAS) – https://ec.europa.eu/health/sites/health/files/scientific_committees/consumer_safety/docs/sccs_o_228.pdf
- Synthetic Amorphous Silica (SAS) industry response to the opinion of the Scientific Committee on Consumer Safety (SCCS) on silica in cosmetics with regard to solubility – https://www.asasp.eu/images/Publications/ASASP1101b_-_ASASP_response_to_solubility_SCCS_Opinion_Dec_2019_final.pdf