PHMB in food: ingestion safety

What is phmb?

The IUPAC name is 1,1'-hexamethylenebis[5-methyl-2-piperidone] or polyhexamethylene biguanide hydrochloride.

Also known as: 1,1'-hexamethylenebis[5-methyl-2-piperidone] or polyhexamethylene biguanide hydrochloride, polyhexamethylene biguanide, PHMB HCl, Cosmocil CQ.

IUPAC name

1,1'-hexamethylenebis[5-methyl-2-piperidone] or polyhexamethylene biguanide hydrochloride

CAS number

32289-58-0

Molecular formula

C7H17N5O2·HCl

Molecular weight

194.67 g/mol

SMILES

C1=CC=C(C(=C1)C(=O)O)NC2=CC=CC=C2C(=O)O

PubChem CID

11371

Regulatory consensus

2 regulatory and scientific bodies have classified PHMB. The classifications differ — that's the data.

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where you encounter phmb

• contact lens solutions
• wound care
• oral antiseptics
• water treatment
• pool disinfection

Safer alternatives

Lower-risk approaches that achieve a similar outcome to PHMB:

• Physical preservation methods (UV treatment, filtration, controlled atmosphere)
  Trade-offs: Removes 95-99% of dissolved contaminants including metals, PFAS, nitrates; wastes 2-4 gallons per gallon produced (improving with newer systems); removes beneficial minerals; $0.05-0.25/gallon; requires pre-treatment for longevity.
  Relative cost: 1.2-2×
• Naturally-derived antimicrobials (essential oil components at validated concentrations)
  Trade-offs: Removes 95-99% of dissolved contaminants including metals, PFAS, nitrates; wastes 2-4 gallons per gallon produced (improving with newer systems); removes beneficial minerals; $0.05-0.25/gallon; requires pre-treatment for longevity.
  Relative cost: 2-5× conventional
• Hurdle technology combining multiple mild preservation methods
  Trade-offs: Alternative approach; specific tradeoffs depend on application context, scale, and regulatory requirements. Full hazard assessment of alternative recommended before adoption to avoid regrettable substitution.
  Relative cost: 1.2-2×

Frequently asked questions