Parabens synergists

Imidazolidinyl urea kills gram-negative bacteria. It acts synergistically with parabens to provide a broad-spectrum antibiotic that is effective against mold, yeast, and bacteria. The combination of the two chemicals constitutes the most widely used preservative in cosmetics. 

Parabens kill molds and fungi. They are used synergistically with bactericides to make broad-spectrum antimicrobials. 

Butylparaben is thus more active than methylparaben. Activity may be improved by using combinations of parabens since synergistic effects occur. Activity has also been reported to be improved by the addition of other excipients see Methylparaben for further information. 

The activity of the parabens increases with increasing chain length of the alkyl moiety, but solubility decreases. Activity may be improved by using combinations of parabens since synergistic effects occur. Ethylparaben is commonly used with methylparaben and propylparaben in oral and topical formulations (such mixtures are commercially available for example, Nipasept (Nipa Laboratories Inc.). Activity has also been reported to be improved by the addition of other excipients see Methylparaben for further information. 

Imidurea is a broad-spectrum antimicrobial preservative used in cosmetics and topical pharmaceutical formulations typical concentrations used are 0.03-0.5% w/w. It is effective between pH 3-9 and is reported to have synergistic effects when used with parabens see Section 10. 

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