Formaldehyde is classified as a known human carcinogen by three separate agencies: the International Agency for Research on Cancer (IARC), the National Toxicology Program (NTP), and the EPA. You will rarely see "formaldehyde" on a product label. What you will see are DMDM Hydantoin, Quaternium-15, Bronopol, and Imidazolidinyl Urea. These are formaldehyde releasers, preservatives designed to slowly release formaldehyde over a product's shelf life. That is not a side effect. It is the intended mechanism. No Nines™ products are formulated without formaldehyde releasers of any kind, as defined by the No Nines™ Standard™.
What are formaldehyde releasers?
Formaldehyde releasers are a class of preservatives that function by gradually releasing small amounts of formaldehyde gas into a product over time. Formaldehyde itself is the antimicrobial agent; the releaser is simply a delivery mechanism. These compounds are designed to be chemically unstable. That instability is the feature, not the flaw. As the compound breaks down, it releases formaldehyde, which prevents microbial growth in the product.
The release is continuous. From the moment the product is manufactured through its entire shelf life, formaldehyde is being generated. The rate varies by compound and by conditions such as temperature and pH, but the process does not stop until the releaser is fully depleted.
The most common formaldehyde releasers found in household and personal care products include:
DMDM Hydantoin is one of the most widely used formaldehyde-releasing preservatives in shampoos, conditioners, body washes, and liquid hand soaps. Quaternium-15 releases more formaldehyde per unit than most other releasers and is the most common formaldehyde-releaser sensitizer in the United States, with a reported sensitization rate of 7.7% among dermatitis patients, according to a 2022 clinical review in Contact Dermatitis. Bronopol (2-Bromo-2-nitropropane-1,3-diol) is found in cleaning products, cosmetics, and industrial applications. Imidazolidinyl Urea and Diazolidinyl Urea appear in both cleaning products and cosmetics. Sodium Hydroxymethylglycinate is sometimes marketed as a milder alternative, but it releases formaldehyde through the same mechanism.
On a product label, you will never see "formaldehyde-releasing preservative." You will see one of the names above. The connection between the ingredient name and its function is not obvious to consumers, which is part of the problem.
What the research says
The carcinogenicity of formaldehyde itself is not a matter of scientific debate among the agencies that evaluate it. IARC classified formaldehyde as a Group 1 carcinogen (the highest classification, meaning "carcinogenic to humans") in 2004, with sufficient evidence linking it to nasopharyngeal cancer. In 2009, IARC reaffirmed its classification and extended it, concluding there was also sufficient evidence linking formaldehyde to myeloid leukemia.
The NTP first listed formaldehyde as "reasonably anticipated to be a human carcinogen" in 1981. In its 12th Report on Carcinogens (2011), the NTP upgraded formaldehyde to "known to be a human carcinogen," citing sufficient evidence from studies on nasopharyngeal cancer, sinonasal cancer, and myeloid leukemia. The National Academy of Sciences independently reviewed this assessment in 2014 and concurred with the listing.
The EPA finalized its IRIS Toxicological Review of Formaldehyde in August 2024, concluding that formaldehyde is "carcinogenic to humans by the inhalation route of exposure." The EPA's cancer risk guidelines use a linear no-threshold model for genotoxic carcinogens like formaldehyde, meaning the agency does not assume a safe exposure level exists.
Three independent agencies, IARC, NTP, and the EPA, have each concluded that formaldehyde is a known or confirmed human carcinogen.
The industry argument for formaldehyde releasers centers on concentration: the amount of formaldehyde released by these preservatives is small, typically below 0.1% in a finished product. However, this argument has several problems. First, exposure is cumulative. A person using shampoo, hand soap, body wash, and a cleaning product that each contain a formaldehyde releaser is exposed multiple times per day, across years. Second, formaldehyde causes contact sensitization at low concentrations. A 2025 systematic review and meta-analysis published in Contact Dermatitis found a pooled prevalence of formaldehyde contact allergy of 2.88% among patch-tested patients, with clinical relevance in 41.57% of those cases. Third, for genotoxic carcinogens, the standard toxicological approach does not recognize a safe threshold, because the mechanism of harm operates at the DNA level.
These concerns are not theoretical. In 2021, a class action lawsuit was filed against Johnson & Johnson over DMDM Hydantoin in its OGX brand shampoos, alleging the formaldehyde-releasing preservative caused hair loss and scalp irritation. The lawsuit also noted that Johnson & Johnson had publicly committed in 2012 to phase out formaldehyde-releasing preservatives from its personal care products by 2015, then acquired the OGX brand in 2016 without removing the ingredient. The European Union has moved to restrict formaldehyde and certain formaldehyde releasers, including quaternium-15, in cosmetic products.
Where formaldehyde releasers show up in your home
Formaldehyde releasers are not confined to a single product category. They appear across personal care, cleaning, and cosmetic products. Understanding where they show up is important because cumulative exposure is the real concern.
Baby wash and shampoo. DMDM Hydantoin has been used as a preservative in products marketed for infants. These products are used daily on developing skin and are often applied in warm, enclosed bathrooms where any released formaldehyde concentrates in the air.
Liquid hand soap. Quaternium-15 and DMDM Hydantoin are common preservatives in liquid hand soaps. Hands are washed multiple times per day, creating repeated skin contact with released formaldehyde.
Body wash and shampoo. These represent some of the highest-volume applications for formaldehyde releasers, used daily in warm water that can accelerate the release of formaldehyde from the preservative compound.
Cleaning wipes and multi-surface cleaners. Formaldehyde releasers preserve these products during their shelf life. When you use a cleaning wipe, you are spreading the preservative (and the formaldehyde it releases) across surfaces in your home.
Laundry detergent. Some liquid laundry detergents contain formaldehyde releasers. Residues can remain on fabric after washing, creating ongoing skin contact with clothing, towels, and bedding.
Cosmetics. Foundations, moisturizers, and other leave-on cosmetics may contain formaldehyde releasers. Leave-on products present extended skin contact compared to rinse-off products.
Pet shampoo. Formaldehyde releasers appear in pet grooming products as well. Pet owners handle these products directly, and pets are exposed through skin contact during and after bathing.
The pattern is clear: these are not niche industrial chemicals. They are in products used daily, often on skin, often in enclosed spaces, and often across multiple product categories simultaneously.
What No Nines uses instead
The No Nines approach to preservation does not require formaldehyde releasers because the formulas are designed differently from the start.
The majority of No Nines products are built on hypochlorous acid (HOCl), which is inherently antimicrobial. Products like the Whole Home HOCl Cleaner, Pet Deodorizer, Sink + Drain Refresher, and Washer Refresh are self-preserving. HOCl does not need a secondary preservative to prevent microbial contamination because it is itself an antimicrobial compound. This eliminates the need for formaldehyde releasers entirely in these products.
For products that are not HOCl-based, the approach is simple formulation with alternative preservation. The Foaming Hand Wash uses a plant-based surfactant system with preservation that does not rely on formaldehyde release. The Baby Skin Mist is formulated without formaldehyde releasers. Every No Nines product, whether it is a surface cleaner, a Laundry Rinse, or a Face + Body Mist, excludes formaldehyde releasers as a category.
The underlying principle is that simpler formulas need fewer preservatives. When a product contains fewer ingredients that could support microbial growth, the preservation challenge is smaller. This makes it possible to avoid formaldehyde releasers without compromising shelf stability.
The bottom line
Formaldehyde is classified as a known human carcinogen by three independent agencies. Formaldehyde releasers are preservatives specifically designed to release formaldehyde. The connection between the two is not ambiguous; it is the stated function of these ingredients.
These preservatives appear in products used on skin, on surfaces, and on clothing, often multiple times per day. They are listed on labels under names that do not communicate their function to most consumers. And the cumulative exposure across product categories is rarely considered.
No Nines products are formulated without formaldehyde releasers. This is one of the nine chemical categories excluded under the No Nines Standard, and it reflects a straightforward position: when three major health agencies agree that a substance causes cancer, and an ingredient is designed to release that substance, the ingredient should not be in household or personal care products.
If you want to check whether products in your home contain formaldehyde releasers, look for DMDM Hydantoin, Quaternium-15, Bronopol, Imidazolidinyl Urea, Diazolidinyl Urea, or Sodium Hydroxymethylglycinate on the ingredient label.
See every ingredient in every No Nines product.
This is post 7 of 9 in the Nasty Nine series. Read more about ethanolamines in cleaning products (Post 5) and phthalates in cleaning products (Post 3).
