Imidazolidinyl urea

Imidazolidinyl urea is a synthetic cosmetic preservative made from allantoin and formaldehyde. It is a white, free-flowing powder that dissolves easily in water and has little smell.

• Formula: C11H16N8O8
• CAS number: 39236-46-9
• Molar mass: about 388.3 g/mol
• Type: formaldehyde-releasing preservative

It is mainly effective against bacteria and is weaker against yeasts and moulds, which is why formulators usually combine it with a second preservative.

Azlok sells Imidazolidinyl Urea (Imid Urea), listed under cosmetic raw ingredients, so it is cosmetic grade. The product name doesn't give a pack size; check the listing for weights. See today's price per kg.

• Creams, lotions and body butters that contain water.
• Shampoos, conditioners and body washes.
• Gels, toners and some colour cosmetics such as foundations.
• Usually paired with methylparaben and propylparaben, or with other preservatives, to cover yeasts and moulds.

It is not used in anhydrous products such as balms and oils, which don't contain water and usually need no preservative of this type. It is also less common in products marketed for babies or very sensitive skin, where formulators often choose preservatives that don't release formaldehyde.

Published supplier ranges are typically 0.2 to 0.5% of the finished product. The EU allows it up to 0.6%; check current BIS and CDSCO rules for products sold in India.

1. Weigh it accurately; 0.3% means 0.3 g in 100 g.
2. Dissolve it in a little water.
3. Add it during cool-down, below about 40 °C, as most supplier sheets suggest.
4. Add a second preservative for yeast and mould cover, following its own use level.
5. Check the final pH; it works across a wide range, roughly pH 3 to 9.

A preservative doesn't replace clean equipment. Wash and dry jars and tools well, wipe them with alcohol, use distilled or boiled and cooled water, and get a preservative efficacy (challenge) test done on products before selling them. Write the preservative and its percentage on your batch record every time.

• It releases formaldehyde, a known skin sensitiser. Some people react to formaldehyde-releasing preservatives, so patch test every product and consider other preservatives for sensitive-skin or baby products.
• Avoid breathing the dust; wear gloves and safety glasses when weighing.
• Store tightly closed in a cool, dry place; it absorbs moisture.
• Keep away from strong oxidisers and strong acids.
• Keep away from children.

Cosmetic grade is the only grade you need for creams and shampoos. Use is so low that a small pack lasts most home and small-brand formulators a long time; 100 g preserves roughly 20 to 50 kg of product at typical levels. Buy fresh rather than stockpiling. Keep the supplier's specification and certificate of analysis with your batch records. For 25 kg and above, use the bulk inquiry form.