Common Name(s): Hexanedioic acid,butanedicarboxylic acid

CAS Number: 0124-04-09

DESCRIPTION

What It Does: Adjusts and stabilizes formulation ph; provides mild exfoliant activity at higher concentrations.

Why It's Used: Mild, food-approved ph adjuster and buffer in formulations where tartaric or citric acid may be too reactive.

How It Works: Donates protons in sequence (two pka values: 4.43 and 5.41) providing excellent buffering capacity across broad ph range. two carboxylate groups enable metal chelation.

Typically Found In: Formulation ph adjustment,mild exfoliants

TECHNICAL DETAILS

Primary Category: Functional ingredient – dicarboxylic acid / ph adjuster

Secondary Functions: Ph buffer,chelating agent

Application Areas:

Typical Concentration Range: 0.1%–3%

SOURCING & ETHICS

Vegan Status: Yes – synthetic

Halal Status: Yes

Source Notes: Produced synthetically by oxidation of cyclohexane. gras food additive (e355).

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Moderate tolerability; introduce gradually. some photosensitization.

Safe for Sensitive Skin: Use with caution – spf advised

SAFETY & COMPATIBILITY

Safety Profile: Good safety profile at recommended concentrations. spf recommended. ewg score: 1–2.

Works Well With: Ceramides,niacinamide,hyaluronic acid,spf

Avoid Combining With: Multiple exfoliating acids simultaneously; high concentrations without spf

SCIENTIFIC NOTE

Adipic acid's two sequential pka values (4.43 and 5.41) provide better buffering capacity across the cosmetically relevant ph range 4–6 compared to single-pka acids, making it an efficient ph stabilizer for formulations targeting specific active ph windows.

Last Verified: Cosing database,cir safety assessment

Primary Sources: 2026-03-12