Dimethyloldimethyl Hydantoin (DMDMH): Formaldehyde-Releasing Preservative

Technical Introduction

Dimethyloldimethyl hydantoin (DMDMH) is a formaldehyde-releasing biocide widely used as a preservative in cosmetics, personal care, household, and industrial products. It belongs to the family of imidazolidinyl/formaldehyde derivatives, which gradually release small amounts of free formaldehyde in aqueous systems, effectively controlling microbial growth.

• Chemical Name: 1,3-bis(hydroxymethyl)-5,5-dimethylhydantoin

• CAS Number: 6440-58-0

• Mechanism of Action: Slowly releases formaldehyde, which penetrates microbial cells, denatures proteins, and inhibits microbial enzymes, leading to effective control of bacteria, fungi, and yeasts.

• Form: Usually supplied as 55% aqueous solution.

Applications

• Cosmetics & Personal Care

  • Shampoos, conditioners, hair gels

  • Lotions, creams, moisturizers

  • Makeup products

  • Deodorants

  • Baby products (restricted in some regions)

• Household & Industrial Products

  • Detergents, liquid soaps

  • Paints, adhesives, glues

  • Industrial water treatment

  • Cleaning products

• Textile & Leather Processing

  • Acts as an antimicrobial preservative in finishing formulations.

✅ Advantages

• Broad-spectrum antimicrobial action against bacteria, yeast, and fungi.

• Stable in wide pH range (3–9) → suitable for cosmetics and cleaning products.

• Cost-effective preservative system.

• Compatible with surfactants, emulsifiers, and many cosmetic ingredients.

• Low use levels provide strong protection against microbial contamination.

⚙️ Specifications (Typical Technical Parameters)

⚠️ Safety & Regulatory Notes

• Regulations:

  • Approved for use in cosmetics at maximum 0.6% active ingredient (EU Cosmetic Regulation, FDA, ASEAN).

  • Must comply with formaldehyde limits in finished products (EU: ≤0.2% free formaldehyde).

• Safety Concerns:

  • Can release trace formaldehyde, a potential irritant and allergen in sensitive individuals.

  • Not suitable for products intended for use on mucous membranes or infants under 3 years in EU.

• Labeling: Products containing DMDMH that may release >0.05% free formaldehyde must be labeled “contains formaldehyde” in EU.

❓ FAQ

Q1: Is DMDMH safe in cosmetics?
Yes, within regulated limits (≤0.6%). However, sensitive skin types may experience irritation due to formaldehyde release.

Q2: What types of microbes does DMDMH protect against?
It provides broad-spectrum protection, including Gram-positive & Gram-negative bacteria, fungi, and yeast.

Q3: Can DMDMH be combined with other preservatives?
Yes, it is often used in preservative blends with parabens, phenoxyethanol, or isothiazolinones for synergistic effects.

Q4: Does DMDMH accumulate in the body?
No, formaldehyde released from DMDMH is rapidly metabolized to formate and excreted. At cosmetic use levels, systemic exposure is minimal.

Q5: Why do some brands use “paraben-free” but still keep DMDMH?
Because DMDMH is not a paraben, it allows manufacturers to market products as “paraben-free” while still maintaining microbial stability.