The Anatomy of a Formula—Antiperspirant Sticks, Soft Solids and Gels

By: Eric S. Abrutyn, TPC2 Advisors Ltd., Inc.

Posted: May 4, 2009, from the May 2009 issue of Cosmetics & Toiletries.

Editor’s Note: Cosmetics & Toiletries magazine is pleased to welcome this new quarterly column, “Anatomy of a Formula,” by Eric Abrutyn to its regular lineup. This column dissects current formulas on the market to examine what ingredients are in them and why.

Deodorants have been used for more than 5,000 years, with every major civilization having left a record of efforts to mask body odors. The early Egyptians, for example, recommended application of perfumed oils such as citrus and cinnamon preparations. Over time, applications have evolved from masking offensive odors with simple perfumed oil, to today’s complex deodorant and antiperspirant (AP) applications.

APs have been around for more than 100 years. The first commercial deodorant, Mum, was patented in 1888 by an unknown inventor, and the first antiperspirant with aluminum chloride, Ever-Dry, was produced 15 years later.¹ Since that time, APs have morphed in the complexity of their delivery systems and associated actives—from simple pads and squeeze bottles with astringent acidic compounds, to more sophisticated sticks and soft solids that use a buffered active.

Each AP form and active change has been initiated either by: 1) a technological breakthrough-e.g., roll-ons evolving from the invention of the ball-point pen, or polymeric hydrated aluminum oxides evolving from the molecular manipulation of simple aluminum chloride; 2) regulatory requirements such as the development of solid sticks resulting from a ban on fluorocarbon propellants; or 3) a marketing claim for the novel use of a technology or a unique delivery system; for instance, the “clinical strength” claim originating from the advent of drug labeling requirements.

Although sticks are the most popular form of APs, they are not necessarily the ideal form to deliver the highest level of efficacy. This is due to the fact that water-soluble AP actives must transport through a hydrophobic waxy matrix, slowing the process of delivery to the eccrine gland. Extrudable, opaque, creamy soft solids deliver higher levels of efficacy because their lower amounts of hydrophobic, waxy ingredients improve the availability of the active to the sweat glands. Extrudable, clear gel solids deliver lower efficacy because their silicone polyether w/o emulsifiers are believed to inhibit the availability of actives to the sweat glands.