California has enacted a new law requiring manufacturers of children’s diapers to disclose intentionally added ingredients online and on product packaging, introducing new transparency and labeling requirements for the US diaper market from 2029.

Governor Gavin Newsom signed Assembly Bill 1901 (AB 1901) on September 28, 2026. The law applies to children’s diapers sold, distributed or manufactured in California and establishes requirements covering both digital ingredient disclosure and product packaging.

What manufacturers will have to disclose

By January 1, 2029, manufacturers must publish a list of all intentionally added ingredients for their children’s diapers on a dedicated webpage on the manufacturer’s website. The law also permits the information to be displayed on the product-details page of websites where the diapers are sold.

For each ingredient, manufacturers must provide:

• the chemical or raw-material name;
• the Chemical Abstracts Service (CAS) number; and
• all specific functions or purposes for which the ingredient is used in the diaper.

The information must be presented in order of chemical or raw-material weight, with the ingredient name, CAS number and function shown together.

The definition of children's diapers is broad and covers disposable briefs, protective underwear, liners, boosters, inserts and underpads designed for children.

Packaging requirements

The law introduces packaging requirements in two stages:

From January 1, 2029, children's diapers distributed or manufactured in California must carry, on the outermost package, a publicly identifiable list of intentionally added ingredients together with the internet address of the manufacturer's dedicated disclosure webpage.

From July 1, 2029, children's diapers sold in California must carry the same information on the outermost package.

The distinction means manufacturers will need to account for the earlier January deadline when producing or distributing products in the state, rather than treating July 2029 as the sole packaging compliance date.

Enforcement and penalties

The California Department of Toxic Substances Control (DTSC) is authorized to enforce the requirements and may adopt regulations to implement and interpret the law.

Companies violating the requirements can face an administrative penalty of up to $5,000 for a first violation and $10,000 for each subsequent violation. Penalties may also be assessed for each day a continuing violation remains in place.

The law also prohibits the sale, distribution or manufacture in California of children's diapers that do not comply with the requirements.

Industry and confidentiality considerations

For diaper manufacturers, the requirements introduce additional work around ingredient mapping and supply-chain data management, particularly for products containing multiple polymers, adhesives, fragrances, additives and other intentionally added substances.

The disclosure requirements also raise questions around commercially sensitive formulation information. This is relevant because manufacturers will have to identify individual chemical or raw-material identities, CAS numbers and functions rather than simply providing broad ingredient categories.

The legislation's supporters have framed the measure as a way of giving parents greater visibility into the materials used in children's diapers. Assemblymember Marc Berman, who introduced AB 1901, said the law is intended to provide consumers with information about the ingredients used in products worn by children.

Part of a wider US labeling trend

California is not the first US state to introduce diaper ingredient-labeling requirements.

New York enacted its diaper-labeling law in December 2024. It requires packages or boxes containing diapers sold in the state to carry a printed list of ingredients in order of predominance. The law covers disposable and reusable diapers.

Illinois subsequently enacted its Diaper Labeling Act, effective January 1, 2027. It requires packages or boxes of diapers sold in the state to carry a printed ingredient list in order of predominance. Ingredients present at 1% or less may be listed in any order, while manufacturers may use a common or functional name instead of the specific chemical identity when an ingredient qualifies as confidential or a trade secret under applicable law.

California's approach differs by combining on-pack disclosure with a dedicated online disclosure system, while requiring the CAS number and specific function or purpose of each intentionally added ingredient.

Implications for diaper manufacturers

For manufacturers supplying the California market, the new requirements will require preparation well ahead of the 2029 deadlines. Companies will need to establish systems for identifying intentionally added ingredients across products and suppliers, maintaining CAS-number and function information, updating online disclosures when formulations change, and incorporating the required information into packaging artwork.

The differing requirements across states could also increase the complexity of managing diaper labeling for manufacturers supplying multiple US markets. Companies may need to determine whether to maintain state-specific packaging and disclosure systems or adopt broader ingredient-transparency processes across their product portfolios.

AB 1901 therefore adds another regulatory consideration for the US hygiene products sector, with California joining a growing number of states requiring greater disclosure of diaper ingredients.