Formulation and evaluation of antiperspirants

 

1. Formulation of Antiperspirants

Antiperspirants are cosmetic products designed to reduce perspiration by temporarily blocking sweat glands. The formulation involves a combination of active ingredients and a base that ensures stability, effectiveness, and ease of application. Here’s a breakdown of key components:

A. Active Ingredients

These are substances that control sweat production by temporarily occluding the sweat glands.

• Aluminum Compounds: The most common active ingredients are aluminum salts, such as:
  • Aluminum chlorohydrate (ACH)
  • Aluminum zirconium tetrachlorohydrex glycine (AZAG)
  • Aluminum chloride These compounds form a gel-like plug within the sweat ducts, which reduces the flow of sweat to the skin surface. Once the plug is formed, it is naturally expelled over time.

B. Base Ingredients

• Emollients and Moisturizers: To prevent skin irritation and provide smooth application (e.g., cyclopentasiloxane, dimethicone).
• Solvents: Used to dissolve active ingredients and help with uniform application. Water or alcohol can be used.
• Carriers: These ensure that the active ingredients are delivered to the skin. In sticks or gels, they may include silicones or esters.
• Fragrances: Added for pleasant scents to mask body odors.
• Preservatives: Prevent microbial contamination and extend shelf life.

C. Product Forms

Antiperspirants come in several forms:

• Sprays: Use aerosolized particles for a quick-drying application.
• Roll-ons: Offer liquid or lotion-based formulas in a roll-on format.
• Sticks: Solid formulations that apply a thin layer of antiperspirant.
• Gels: Water-based products that feel cool and dry quickly on application.

2. Evaluation of Antiperspirants

The efficacy and safety of antiperspirants are evaluated through various testing methods:

A. Efficacy Testing

Efficacy is tested to determine how well the product reduces sweating. The methods include:

1. Gravimetric Testing: This involves measuring the weight of sweat produced by a subject under controlled conditions, both before and after product application. Typically, the underarm area is washed, dried, and then treated with the antiperspirant. Subjects may undergo sweating stimulation through heat or exercise, and the amount of sweat is collected on absorbent pads and weighed.
2. Vapometer Method: This measures the rate of moisture vapor loss from the skin using a specialized instrument. It can help in determining the reduction in sweat release after using an antiperspirant.
3. Subjective Feedback: Test panels evaluate product comfort, drying time, residue, and odor control through surveys or diaries.

B. Safety Testing

• Skin Irritation Testing: This is conducted to ensure the product does not cause irritation, redness, or allergic reactions. Patch testing is commonly used, where small amounts of the product are applied to the skin under controlled conditions to observe any adverse reactions.
• Microbial Testing: To ensure that the product formulation resists bacterial growth, especially for water-based formulations.

C. Stability Testing

• Shelf Life: Antiperspirants are tested for physical and chemical stability over time. This includes exposure to varying temperatures and humidity levels to assess any changes in the product's texture, efficacy, or appearance.
• Packaging Compatibility: The product should remain stable within its packaging material without interacting with it. Tests are conducted to ensure the packaging doesn’t degrade or leach chemicals into the product.

D. Regulatory Testing

Depending on the country, antiperspirants may be classified as drugs (due to their physiological effect of blocking sweat). Therefore, they must meet certain regulatory guidelines. In the United States, for instance, the Food and Drug Administration (FDA) oversees antiperspirants as over-the-counter (OTC) drugs, requiring proper labeling and adherence to efficacy standards.

Conclusion

The formulation of antiperspirants involves selecting appropriate active ingredients like aluminum salts, balancing them with base ingredients to ensure skin compatibility, and choosing the product form that best suits consumer needs. Evaluation involves rigorous testing to ensure efficacy, safety, stability, and regulatory compliance.