Common Name(s): Magnesium octadecanoate,magnesium soap
CAS Number: 557-04-0
DESCRIPTION
What It Does: Provides superior slip and adhesion in cosmetic powder formulations with white colour advantage.
Why It's Used: Premium slip agent for powder cosmetics โ provides superior slip and adhesion vs zinc stearate with whiter colour for formulations where warmth of zinc stearate tint is undesirable.
How It Works: Magnesium soap provides slip and adhesion similar to zinc stearate. slightly higher melting point for better heat stability. whiter colour (less yellow tint than zinc stearate) for brightness-sensitive formulations. also used as tablet lubricant in oral supplement tablets (same cosmetic ingredient).
Typically Found In: Premium powder cosmetics,supplement tablets
TECHNICAL DETAILS
Primary Category: Functional ingredient โ magnesium soap
Secondary Functions: Skin conditioning
Application Areas:
Facial Skincare
Body Care
Hair Care
Beard Care
Color Cosmetics (Makeup)
Dietary/Oral Supplements
Typical Concentration Range: 0.5%โ10%
SOURCING & ETHICS
Vegan Status: Conditional - feedstock declaration required
Halal Status: Unverified - feedstock declaration required (plant, animal and petrochemical routes all exist)
Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier. [audit 2026-07-29 rev2: origin-dependent: the same inci exists in plant, animal and petrochemical versions and the name does not discriminate. determination requires shariah-panel sign-off.]
SKIN COMPATIBILITY
Irritancy Rating: 1/5 โ very low
Comedogenicity Rating: 0/5 โ non-comedogenic
Sensitivity Concerns: Well-tolerated by most skin types.
Safe for Sensitive Skin: Yes
SAFETY & COMPATIBILITY
Safety Profile: Good safety profile at recommended concentrations. ewg score: 1โ2.
Works Well With: Standard skincare actives
Avoid Combining With: No known significant incompatibilities
SCIENTIFIC NOTE
Magnesium stearate's magnesium-oxygen coordination (mgยฒโบ ionic radius 0.72รฅ vs znยฒโบ 0.74รฅ) provides nearly identical ionic bonding to zinc stearate, explaining their similar cosmetic performance. the different visual properties (whiter mg vs warmer yellow zn) arise from different d-orbital filling: mg has no d electrons (colourless) vs zn's fully filled dยนโฐ configuration (also colourless but with subtly different light scattering from the denser znยฒโบ ion).
Last Verified: 2026-03-12
Primary Sources: Cosing database,cir safety assessment