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ISOBUTYRIC ACID.

Questionable CAS 79-31-2 / BUFFERING

Isobutyric acid is a short-chain fatty acid primarily recognized in personal care for its role as a functional ingredient, rather than an active compound. It commonly functions as an emulsifier, fragrance or masking agent, and preservative within cosmetic formulations.

Emulsifying agent Fragrance ingredient Masking agent Preservative Buffering agent

Science

Isobutyric acid contributes to product texture and scent in personal care formulations, acting as an emulsifying agent to stabilize mixtures and as a fragrance or masking agent. While its isomer, butyric acid, has demonstrated anti-inflammatory activity in specific cellular and animal models via HDAC inhibition and FFAR2 receptor modulation, these mechanisms are distinct and not attributed to isobutyric acid.


Research

Low confidence
Effective range N/A
Optimal

N/A


Transparency

Not commonly dusted

Isobutyric acid is not commonly 'dusted' as an active ingredient due to a lack of direct clinical evidence supporting specific skin benefits. Its primary utility lies in its functional properties within a formulation.


The Formula

Solubility
Both
Optimal pH N/A
0 7 14

Stability

With a pKa of 4.84 at 20 °C, isobutyric acid's ionization state shifts significantly around this pH, primarily existing in its anionic form within a typical cosmetic pH range of 5-9. It can function as a buffering agent, influencing formulation stability. Optimal storage for the pure substance is in a cool, dry place, providing a shelf life of approximately 2 years.

Conflicts

  • Strong oxidizing agents
  • Strong bases
  • Ingredients sensitive to low pH or strong acids
  • Combining with multiple strong actives or exfoliants (e.g., AHAs, BHAs, Retinoids, Vitamin C) may exacerbate skin irritation or compromise ingredient efficacy due to pH discordance or heightened sensitization.

Safety

CIR Status
Not reviewed
Sensitization risk Moderate

Isobutyric acid is classified as a corrosive substance, capable of causing severe skin burns and eye damage in concentrated form, and may irritate respiratory passages. While these hazards are primarily associated with the concentrated substance, there are no specific CIR or SCCS safety reviews, nor FDA maximum concentrations, for its use as an active ingredient in skincare.


Your Skin

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

Our Assessment

Questionable

As an ingredient lacking direct clinical efficacy for active skin benefits and presenting significant safety concerns in concentrated forms, isobutyric acid's utility in precision skincare is questionable, primarily serving functional roles with a moderate irritancy risk.


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