Aluminum Hydroxide is a mineral-based ingredient primarily utilized as a protective coating for inorganic UV filters and as an opacifying agent. It enhances formula stability by preventing the photocatalytic degradation of mineral sunscreens while simultaneously improving the spreadability of heavy pigments.
- INCI Name:
- Aluminum Hydroxide
- Chemical/Scientific Name:
- Aluminum Trihydroxide
- Common Aliases:
- Hydrated Alumina, CI 77002, Gibbsite
| Category: | Texture Enhancers |
| Source Origin: | Mineral / Synthetic |
| Comedogenic Rating: | 0 |
| Primary Industries: | Cosmetics, Pharmaceuticals, Oral Care |
| Solubility: | Insoluble in water and alcohol |
At a Glance: Properties & Effects
| Texture Enhancement | |
| Formula Stability | |
| Irritation Risk | |
| Comedogenicity |
- Primary Benefits:
- Neutralizes free radicals generated by mineral sunscreens when exposed to UV light.
- Reduces the “whitecast” and graininess of high-pigment formulations.
- Provides a smooth, physical barrier that helps protect the skin from environmental irritants.
- Potential Risks:
- Minimal risk of irritation; generally considered inert and non-reactive on the skin surface.
Biological Action & Cosmetic Profile
This mineral compound functions significantly as a surface treatment for Titanium Dioxide. When Titanium Dioxide is exposed to ultraviolet radiation, it can become photocatalytic, leading to the creation of reactive oxygen species (ROS) that may damage skin cells or degrade the cosmetic formula. Aluminum Hydroxide creates a stable, non-reactive shell around these particles, effectively quenching free radicals before they can interact with the surrounding environment.
Dispersion quality is greatly improved when this substance is present. By modifying the surface energy of pigments like Mica or Iron Oxides, it prevents the clumping or “agglomeration” of minerals. This results in a more uniform application and a lighter, more cosmetically elegant skin-feel, which is often difficult to achieve in purely physical sunscreens.
Dermatological studies confirm that this ingredient does not penetrate the skin barrier. Because it is an insoluble solid with a relatively large molecular structure, it remains on the surface of the stratum corneum. This lack of bioavailability ensures that the aluminum does not enter the bloodstream through topical application, distinguishing it from soluble aluminum salts used in antiperspirants.
Broader Applications & Origins
Manufacturers often pair this ingredient with Stearic Acid, Silica, or Dimethicone to create complex coating systems. These combinations allow mineral sunscreens to be either water-resistant or highly dispersible in oil-in-water emulsions. Beyond sun care, it serves as an opacifier in color cosmetics, helping to achieve full coverage in foundations and concealers without needing excessive amounts of heavier pigments.
Routine Integration
- Synergies:
- Titanium Dioxide: Maximizes UV protection stability and reduces ROS generation.
- Zinc Oxide: Enhances the overall texture and spreadability of mineral-heavy creams.
- Stearic Acid: Often used in tandem to provide a lipophilic coating for better emolliency.
Clinical Consensus & Safety
The Cosmetic Ingredient Review (CIR) Expert Panel and the Scientific Committee on Consumer Safety (SCCS) have both extensively evaluated Aluminum Hydroxide. The consensus remains that it is safe for use in cosmetic products at current concentrations. Because it is chemically inert and has virtually zero dermal absorption, it is suitable even for sensitive or reactive skin types. Regulatory bodies emphasize that the form used in skincare—insoluble particles—poses no systemic health risk compared to the background aluminum exposure found in diet and water.
Is the aluminum in my sunscreen harmful?
No, the aluminum in sunscreens is typically present as Aluminum Hydroxide, an insoluble mineral coating. Unlike soluble aluminum salts, it does not penetrate the skin and is used specifically to make mineral filters safer and more stable.
Does Aluminum Hydroxide cause acne?
This ingredient has a comedogenic rating of 0. It is an inert mineral that does not clog pores or trigger sebum-related breakouts, making it safe for acne-prone skin.
Why is it used in “natural” sunscreens?
It is a mineral found in nature (as the mineral gibbsite), though the cosmetic version is often purified for safety. It is preferred in mineral sunscreens because it allows for high SPF ratings without the “heavy” or “chalky” feel of uncoated minerals.