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BORIC ACID.

Avoid CAS 10043-35-3 / 11113-50-1 / ANTIMICROBIAL, BUFFERING, DENATURANT

Boric Acid functions as an antimicrobial and antifungal agent, also offering weak buffering and preservative properties in formulations. It is primarily known for its inhibitory effects on various bacteria and fungi, including *Candida albicans*.

antimicrobial/antibacterial buffering preservative

Science

It disrupts microbial cellular structure by interfering with enzyme function, inhibiting mitochondrial energy metabolism, and increasing cell wall permeability. This action ultimately leads to the destruction of cell membranes and inhibition of their formation in pathogens.


Research

Low confidence
Effective range 0.5–5%
Optimal

3%

Key findings

  1. 01 A 3% solution effectively inhibits common bacteria and fungi, proving effective against cutaneous *Candida albicans* infection in studies.
  2. 02 While used for skin protection and superficial fungal infections, substantial evidence for its efficacy in these broader applications is generally considered lacking.

Transparency

Not commonly dusted

The Formula

Solubility
Water
Optimal pH N/A
0 7 14

Stability

Boric acid is a weak acid (pKa 9.24) and is stable up to 100 °C, existing primarily as undissociated boric acid at acidic pH. Its water solubility can be enhanced by specific acids and salts like citric acid or potassium chlorides, but decreased by others.

Synergies

  • Hydrochloric acid, citric acid, tartaric acid, potassium chloride, rubidium chloride, potassium nitrate, sodium nitrate, potassium sulfate, sodium sulfate (increase solubility)
  • Borax (increases solubility due to polyborate formation)

Conflicts

  • Alcohols (forms borate esters)
  • Lithium chloride, sodium chloride, mineral acids (decrease solubility)

Safety

CIR Status
Safe with restrictions
Max tested
5%
Pregnancy
Caution
Sensitization risk Unknown

The CIR Expert Panel considers it safe below 5% with restrictions, advising against use on infant or injured skin. However, the EU's SCCS prohibits its use in cosmetics, classifying it as a Category 1B reproductive toxin due to presumed reproductive toxicity in humans. Absorption through skin depends significantly on the vehicle.


Your Skin

No Normal
No Dry
No Oily
No Sensitive
Irritancy Unknown
Comedogenicity Unknown

Our Assessment

Avoid

Due to its classification as a Category 1B reproductive toxin in the EU and its prohibition in European cosmetic products, Boric Acid is not suitable for precision skincare formulations.


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