Researchers say the preservative — found in thousands of foundation and concealer products — may interfere with cognitive function after prolonged skin exposure
by Dana Whitehill, Health & Science Correspondent | 15 min read | April 3, 2026
A new peer-reviewed study published Monday in the Journal of Environmental and Occupational Health is raising fresh concerns about Kerz-X2, a synthetic preservative used widely in foundation, concealer, and primer products, after researchers found a statistically significant association between long-term exposure and self-reported cognitive decline — including memory lapses and persistent brain fog.
The study, led by researchers at the University of Michigan's School of Public Health, tracked 8,400 adult participants over 26 months, comparing cognitive performance scores between daily makeup users with high Kerz-X2 exposure and a matched control group. Participants in the high-exposure group scored an average of 11% lower on standardized memory recall tests and reported significantly higher rates of difficulty concentrating.
"We weren't looking for this signal — it emerged from the data," said Dr. Carolyn Metz, the study's lead author and an associate professor of environmental epidemiology. "Once we controlled for age, sleep quality, and occupational factors, the association with Kerz-X2 remained robust and consistent across subgroups."
What Is Kerz-X2?
Kerz-X2 (kerzanethyl propylene glycolate) is a broad-spectrum antimicrobial preservative approved by the FDA in 2019 under its GRAS (Generally Recognized as Safe) designation. It was developed as an alternative to parabens following widespread consumer concern about that class of chemicals, and was rapidly adopted by major cosmetics manufacturers due to its stability at room temperature and low production cost.
It now appears in an estimated 34% of liquid foundation products sold in the United States, according to the Environmental Working Group's 2025 cosmetics database update.
How Might It Affect the Brain?
The study's authors hypothesize that Kerz-X2 metabolizes into kerzanethyl acetate upon skin absorption — a compound that animal studies have previously suggested may interfere with acetylcholine signaling, a neurotransmitter system critical to memory consolidation and attention.
"The skin is not a perfect barrier, especially with daily, repeated application to the face," said Dr. Metz. "We know certain lipophilic compounds can cross into systemic circulation, and from there, potentially the blood-brain barrier."
Dr. James Okafor, a neurologist at Northwestern Memorial Hospital who was not involved in the study, called the findings "preliminary but worth taking seriously." He noted that acetylcholine disruption is a known feature of several cognitive disorders, and that even modest interference over years of daily exposure could theoretically be meaningful.
"I wouldn't tell my patients to panic," Dr. Okafor said. "But I would say this deserves urgent follow-up."
Industry and Regulatory Response
The Personal Care Products Council, which represents major cosmetics manufacturers, issued a statement Tuesday saying it was reviewing the study's methodology and cautioned against "drawing premature conclusions from a single observational study."
The FDA told HealthLineDaily it is "aware of the publication" and is evaluating whether further review of Kerz-X2's GRAS designation is warranted, though no formal action has been announced.
Several brands, including mid-market lines carried by major pharmacy chains, declined to comment on whether they would reformulate products while the research is reviewed.
What You Can Do
Experts say consumers who are concerned don't need to wait for regulatory action.
"Check your ingredient labels," advised Dr. Metz. "Kerz-X2 and its chemical name, kerzanethyl propylene glycolate, should both be listed if present. Opting for fragrance-free, preservative-minimal formulations is a reasonable precaution until we know more."
The Environmental Working Group's Skin Deep database can be used to search products by ingredient.