In January 2025, clean beauty brand Kosas was served with a formal notice of intent to sue over allegations that one of its mascaras contained trace levels of chemicals classified as potential carcinogens under California law. The notice, filed under the state’s Proposition 65 framework, accuses the company of failing to provide adequate warnings to consumers about exposure to certain substances detected in product testing.
The development has triggered renewed scrutiny of ingredient transparency in the beauty industry — particularly among brands that market themselves as “clean,” “non-toxic,” or health-conscious.
The Allegations
Independent lab tests allegedly found trace quantities of a carcinogenic compound in KOSAS mascara, as per the notice. Although the levels reported were allegedly low, the suit claims that the presence of the compound exceeded the threshold requiring a warning under Proposition 65, California’s Safe Drinking Water and Toxic Enforcement Act.
Proposition 65 requires businesses to give clear and reasonable warnings when their products expose consumers to chemicals deemed carcinogenic, a cause of birth defects, or reproductive harm, as determined by the State of California. Legal action based on this law has resulted from thousands of consumer complaints across multiple industries, including food/beverage and cosmetics.
While the complaint does not allege that using the mascara can cause cancer, it does allege that Kosas failed to warn consumers about their exposure, amounting to high levels of a listed chemical exceeding regulatory limits.
Company Response
Following the publication of the notice, Kosas immediately issued a statement reiterating their commitment to the safety and regulatory compliance of their products. To evaluate the claims, Kosas also indicated that they were conducting an independent review of the claims and performing independent testing.
“We are committed to the safety of our products and to the integrity of the formulations,” Kosas’ statement said. “Our consumers are our top priority.”
Kosas explained that in the United States, cosmetics are regulated by federal law and must be manufactured according to federal safety standards before they can be sold. Kosas also indicated that trace contaminants may be present in their raw materials, although they have strict supplier screening procedures in place, as such contaminant levels are usually not considered to be dangerous by the federal government.
Clean Beauty Under the Microscope
The situation has sparked particular debate because Kosas is widely recognized as part of the “clean beauty” movement — a sector that emphasizes ingredient transparency and the exclusion of certain controversial chemicals.
Critics argue that clean beauty branding can create heightened expectations. When a brand positions itself as safer or more natural than competitors, even minor compliance issues may provoke a stronger consumer reaction.
Industry experts note that trace amounts of heavy metals and other environmental contaminants can be found in many cosmetics, often due to naturally occurring elements in mineral-based pigments. Regulatory agencies generally assess risk based on exposure levels rather than the mere presence of a substance.
Legal and Financial Implications
Companies usually have sixty days to reply to a notice of intention to sue under Proposition 65. During this time, these companies may be able to negotiate a settlement, reformulate a product, or dispute the validity of the test results.
If the case does go to court, Kosas could be forced to pay fines, place warning labels on their products, and/or reformulate their products. However, many cases under Proposition 65 resolve through settlement (and without a finding by a court of infringement).
According to legal analysts, these types of notices are common in California and serve as a means for complying with the law as opposed to providing evidence of the products being dangerous.
Consumer Reaction
News of the potential lawsuit quickly circulated on social media, with customers expressing a mix of concern and skepticism. Some longtime users of the mascara questioned whether they should discontinue use, while others pointed out that regulatory disputes do not necessarily indicate unsafe products.
Dermatologists and toxicologists interviewed by media outlets cautioned against panic, explaining that risk depends heavily on dosage and frequency of exposure. They emphasized that cosmetic safety assessments consider how products are used in real-world conditions.
Broader Industry Context
The case underscores the complex regulatory landscape facing beauty brands in 2025. While federal oversight of cosmetics has expanded in recent years, state-level laws like Proposition 65 add another layer of compliance requirements.
For companies operating nationwide, meeting varying thresholds across jurisdictions can pose logistical and legal challenges.
At the same time, consumers are increasingly attentive to ingredient lists and third-party testing reports. Transparency has become a competitive advantage — but it also invites scrutiny.
What Happens Next
As it stands, Kosas has yet to announce whether it will settle or defend itself against allegations, and the final ruling may be determined over the next few weeks by further testing and discussion of legal matters.
This dispute emphasises that clean beauty brands must tread carefully when trying to balance marketing promises with government rules. In a market where safety and transparency are critical attributes to sell to consumers, any allegation, even at a trace level, can lead to considerable damage to their reputation.
Ultimately, over the next few months, Kosas will find out if this issue is resolved as a minor compliance issue or will develop into a much larger challenge to consumer confidence in their company.
