Does DMDM hydantoin really cause hair loss? Here’s what you need to know

DMDM hydantoin, a preservative in shampoos, conditioners and other water-based personal care products, is the focus of several class-action lawsuits against Johnson & Johnson and Unilever claiming exposure to the substance led to hair loss. While there are no studies that link exposure to DMDM hydantoin to hair loss, the preservative is linked to a higher risk for allergic reactions and immunotoxicity.

What is DMDM hydantoin?

DMDM hydantoin is a formaldehyde releaser or donor, meaning it slowly releases the chemical formaldehyde as it breaks down in the product over time to prevent mold and bacteria from growing.  It works by slowing or stopping the growth of potentially harmful microbes such as fungi, yeast and bacteria.

As a result, DMDM hydantoin increases the shelf-life of cosmetics and personal care products. Preservatives are essential for such products that contain water, including shampoos, conditioners and body washes.  

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Health hazards

One study by researchers in Spain found that products with formaldehyde-releasing ingredients could cause allergic contact dermatitis or contact eczema in people allergic to formaldehyde.

A separate study by researchers in the Netherlands also found that an increased use of products with DMDM hydantoin heightened the risk of developing dermatitis and itching in consumers who are already sensitive to formaldehyde exposure.

The Food and Drug Administration lists DMDM hydantoin as a common allergen in personal care products. People who are allergic to formaldehyde may also be sensitive to DMDM hydantoin, since the preservative releases small amounts of formaldehyde.


Health risks from formaldehyde exposure are well-documented, and the National Toxicology Program classifies it as a known carcinogen. Short-term exposure is associated with eye, nose, and throat irritation, shortness of breath and wheezing. Formaldehyde is a potent sensitizer and may increase some groups’ risk of asthma. The Centers for Disease Control and Prevention warns “working with formaldehyde may increase your chances of having fertility problems or a miscarriage.”

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Laws regulating ingredients in personal care products

The U.S. cosmetics industry is notoriously underregulated, and federal cosmetics law was last updated more than 80 years ago.

A new EWG analysis also finds that more than 80 nations have stricter laws that regulate the chemicals used in personal care products.

Some states are not waiting for Congress or the FDA to act. Last year, California became the first state to ban 24 toxic chemicals in beauty products, including formaldehyde. Last month, Maryland passed a similar bill. Regulations to implement the laws in both states will begin in 2025.

A bipartisan group of U.S. senators in June introduced the Personal Care Protection Act to strengthen FDA oversight of personal care product ingredients, but it is still pending.

While these new and proposed laws don’t regulate formaldehyde releasers like DMDM hydantoin, they do ban formaldehyde in personal care products.

Consumer tools

Marketing claims on consumer products like “natural,” “hypoallergenic” or “for sensitive skin” have no federal standard or definition in the U.S. Some products might also claim to be “formaldehyde-free” because companies are not directly adding formaldehyde to the product, even though they are still using formaldehyde-releasing ingredients.

Consumers need to carefully read the ingredients on product labels. Our Skin Deep database includes information and online hazard assessments for hundreds of personal care products that contain DMDM hydantoin. If you’re at the store, check a product’s ingredient information and how it scores with EWG’s Healthy Living app.

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