Ingredient dictionary

Diazolidinyl Urea

Diazolidinyl Urea is a preservative that slowly releases formaldehyde to keep bacteria and mold from growing in water-based products. It is on the label of 4 products in our library. Checked against our library November 6, 2026.

The catch: it belongs to the formaldehyde releaser group, which slowly releases formaldehyde. People with a formaldehyde allergy are usually told to avoid these preservatives too.

Formaldehyde releasers. Preservatives that slowly release formaldehyde, such as DMDM hydantoin and quaternium-15.

What Diazolidinyl Urea does

Stops bacteria from growing in water-based products
Helps keep mold and yeast out
Extends the shelf life of formulas

Diazolidinyl Urea is made by reacting urea with formaldehyde. Once in a formula, it slowly releases small amounts of formaldehyde, which keeps bacteria, yeast and mold from growing. Formulators choose it because it works well in water-based products and is effective against many common microbes.

It is a white, water-soluble powder, so it dissolves easily into lotions, creams and shampoos. It turns up most often in shampoo, where it helps protect water-rich formulas from spoilage.

Good for

Water-based shampoos, lotions and creams that need a preservative to stay safe on the shelf.

Frequently asked questions

Is Diazolidinyl Urea safe?

It is a preservative used in many shampoos and creams. Because it releases formaldehyde, people with a formaldehyde allergy are usually advised to avoid it. Anyone with sensitive skin who notices redness, itching or stinging should stop using the product and speak with a dermatologist.

Why do people with a formaldehyde allergy avoid it?

Diazolidinyl Urea releases formaldehyde as it works, so it falls in the same group. Formaldehyde releasers are grouped together, and people with a formaldehyde allergy are usually told to avoid them too.