Aluminum/Magnesium Hydroxide Stearate is a specialized gelling agent and stabilizer primarily utilized to improve the structural integrity of water-in-oil emulsions. It provides a creamy consistency and enhances the suspension of pigments and mineral filters in cosmetic formulations.
- INCI Name:
- Aluminum/Magnesium Hydroxide Stearate
- Chemical/Scientific Name:
- Aluminum magnesium hydroxide stearate
- Common Aliases:
- Magnesium/Aluminum Hydroxide Stearate, Al/Mg Stearate
| Category: | Texture Enhancers |
| Source Origin: | Synthetic/Mineral (derived from mineral salts and Stearic Acid) |
| Comedogenic Rating: | 0 |
| Primary Industries: | Skincare, Sun Care, Color Cosmetics |
| Solubility: | Oil-dispersible/Insoluble in Aqua |
At a Glance: Properties & Effects
| Texture Enhancement: | |
| Formula Stability: | |
| Irritation Risk: |
Primary Benefits:
- Prevents phase separation in water-in-oil emulsions.
- Enhances the “slip” and spreadability of heavy creams.
- Improves the suspension of mineral sunscreens and pigments.
- Provides a matte finish by reducing the perception of oiliness.
Potential Risks:
- None identified for topical use in standard cosmetic concentrations.
Biological Action & Cosmetic Profile
This mineral-fatty acid complex functions as a rheological modifier, which dictates the flow and structural behavior of a cosmetic product. By forming a microscopic three-dimensional crystalline lattice within the lipid (oil) phase, it prevents the coalescence of water droplets. This mechanism is vital for stabilizing water-in-oil systems, which are traditionally prone to “bleeding” or separating over time. Formulators rely on this ingredient to create rich, protective barrier creams that remain stable in varying temperatures.
The chemical structure combines the properties of Aluminum Hydroxide and magnesium salts with the lipophilic nature of Stearic Acid. This synergy allows the ingredient to coat particle surfaces effectively. In sunscreens, it aids in the uniform distribution of Titanium Dioxide and Zinc Oxide, ensuring that the UV-blocking agents do not clump together. Proper dispersion is essential not only for achieving the labeled SPF rating but also for preventing the “white cast” often associated with mineral filters.
Beyond its stabilizing role, the complex contributes to the sensorial experience of a product. It helps transform the heavy, greasy feel of high-oil formulations into a smoother, more “cushiony” texture. Because it is non-swelling in water, it maintains the integrity of anhydrous (water-free) balms and ointments, providing a consistent thickness that facilitates easy application to the skin.
Routine Integration
Synergies:
- Mineral UV Filters: Optimizes the dispersion of Zinc Oxide for consistent sun protection.
- Emollients: Works alongside Caprylic Capric Triglyceride or Squalane to build viscosity in rich night creams.
- Humectants: Helps lock in Glycerin or Sodium Hyaluronate within a water-in-oil emulsion for prolonged hydration.
Clinical Consensus & Safety
The Cosmetic Ingredient Review (CIR) Expert Panel and the European CosIng database classify this ingredient as safe for use in cosmetic products. Due to its high molecular weight and mineral-organic hybrid structure, it does not penetrate the skin barrier and remains on the surface. Dermatological assessments indicate a negligible risk of irritation or sensitization, even in formulations designed for compromised or sensitive skin. It is considered non-comedogenic, as its function is structural rather than occlusive in a way that would block pores.
Is this ingredient a “heavy metal” or harmful?
No. While it contains aluminum and magnesium in a complexed form, these are stable mineral salts. They are not bioavailable through the skin and do not pose the risks associated with heavy metal toxicity.
Why is it found in “natural” or mineral sunscreens?
It is preferred in mineral sunscreens because it is highly effective at suspending mineral particles like zinc oxide, preventing them from settling at the bottom of the tube or clumping on the skin.