What it is
Polyaminopropyl biguanide is a synthetic cationic polymer belonging to the biguanide family, valued for its activity against a broad range of bacteria and some fungi at low use levels. In sunscreens and other leave-on and rinse-off products it is included to help keep the formula microbiologically stable over its shelf life. It is effective across a wide pH range and is often combined with other preservatives in a preservation system.
Safety & warnings
It is used at low concentrations as a preservative and is generally well tolerated, though sensitive individuals can occasionally experience irritation or contact sensitization, as with many cationic antimicrobials. It is not a fragrance allergen and is not an oil, so comedogenicity is not a relevant concern.
Origin & sourcing
Synthetic. It is a manufactured polymeric biguanide produced through chemical synthesis.
Questions everyone asks
What does polyaminopropyl biguanide do in a sunscreen?
It acts as a preservative, helping to protect the product against microbial growth so the formula stays stable during use.
Is polyaminopropyl biguanide the same as PHMB?
Yes, it is commonly known by the names PHMB, polyhexamethylene biguanide, or polyhexanide, all referring to the same polymeric biguanide preservative.