Stability and Formulation of High-Concentration Antiperspirant Roll-ons

Question

I am looking to create an antiperspirant roll-on product. I have experimented with high concentrations of Aluminum Chlorohydrate (ACH) in two formats: an emulsion and a clear solution.

Emulsion: The product is unstable under accelerated conditions.
Clear Solution: I am unsure which texture modifier to use that can withstand very high concentrations of ACH.

I would like advice in 3 areas:

For the Emulsion format, which Emulsifier should be used to stabilize high concentrations of ACH?
For the Solution format, which texture modifier is compatible with this active ingredient?
Between using ACH alone, Aluminum Zirconium alone, or a combination of both, which option provides the best sweat suppression?

MySkinRecipes Expert · Accepted Answer

To develop a high-performance antiperspirant roll-on that is stable and effective, here are the recommendations for your three specific concerns:

1. Emulsion Form: Recommended Emulsifiers

High concentrations of Aluminum Chlorohydrate (ACH) create a high-electrolyte environment that breaks down most standard emulsions. The industry standard for stable antiperspirant emulsions is the combination of non-ionic emulsifiers:

Steareth-2 (Low HLB)
Steareth-21 (High HLB)

Why this works: This pair is non-ionic, meaning they do not react with the ionic charge of the ACH. Using them together (typically in a ratio like 2:1 or 3:1) creates a robust liquid crystal structure that can stabilize high levels of active ingredients even under accelerated heat conditions.

2. Clear Solution Form: Recommended Thickener

For a clear solution with high ACH, you must use a non-ionic gelling agent. Ionic thickeners (like Carbomer or many natural gums) will immediately clump or fail to thicken in the presence of high salts.

Hydroxyethyl Cellulose (HEC): This is the best choice for a clear, high-electrolyte formula. It provides a smooth, non-sticky texture and remains stable in the acidic pH (around 4.0-4.5) required for antiperspirants.
Recommendation: Use a "Super Clear" grade like Hydroxyethyl Cellulose (HEC) (2000mPa.s) (Super Clear Gel) to ensure the final product is aesthetically pleasing and transparent.

3. Efficacy Comparison: ACH vs. Aluminum Zirconium

When comparing sweat suppression efficacy:

Aluminum Zirconium (AZG): Generally more effective than Aluminum Chlorohydrate. It forms a deeper and more durable "plug" in the sweat duct.
Aluminum Zirconium Octachlorohydrex GLY: This is considered one of the most potent forms of Aluminum Zirconium, specifically designed for "extra strength" or clinical-grade products.
Comparison:
- ACH alone: Good for standard protection, lower irritation potential.
- AZG alone (especially Octachlorohydrex): Highest efficacy for heavy sweating.
- Combination: Often used to balance cost and performance, but a high-grade AZG alone typically outperforms ACH-only formulas.

Summary for Best Performance: If your goal is the highest sweat suppression, Aluminum Zirconium Octachlorohydrex GLY is the superior choice. For the base, use the Steareth-2/21 system for an emulsion or HEC for a clear gel.