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INTRODUCTION

There are entire books, courses, and academic societies dedicated to cosmetic chemistry. This chapter is intended to cover the basics only. Understanding these few basic chemistry items is crucial in order to decipher the language used in reference to personal care products.

COSMETIC INGREDIENT NOMENCLATURE

The cosmetic industry uses nomenclature that differs from that established by the International Union of Pure and Applied Chemistry (IUPAC), which is taught in organic chemistry. The Cosmetic Toiletry and Fragrance Association, which changed its name to the Personal Care Products Council in 2007, compiled a standardized list of ingredients and published it in 1973.1 This system is now known as the International Nomenclature of Cosmetic Ingredients (INCI). A comprehensive description of this system appears in Chapter 4 of Beginning Cosmetic Chemistry.2 Understanding the stem terms facilitates reading product labels. For the most up-to-date information on INCI nomenclature, visit the website for the Personal Care Products Council (http://www.personalcarecouncil.org/). In some cases, the nomenclature varies between the United States (US) and the European Union (EU). Botanical ingredients (those derived from plants), in particular, are labeled differently in the US and the EU. In the EU, the Latin binomial (genus and species names) is used, while in the US the name includes the Latin binominal, the common name of the plant, the plant part, and the type of preparation. Oatmeal extract is a good example to illustrate the divergent approaches to classification. In the EU, the INCI name for oatmeal extract is Avena Sativa. In the US, the INCI name is Avena Sativa (Oat) Kernel Extract. The biggest differences between names in the US and EU seem to be found in the names of botanicals, colorants, denatured alcohols, fragrances, and flavors.3

SIGNIFICANCE OF THE pH

Measurements of pH are used both in formulating and testing product stability. The pH of skin or hair is also a necessary consideration in cosmetic chemistry. pH is the measure of the activity of the hydrogen atom.

Measure of the activity of the hydrogen atom:

pH=log10(aH+)=log10(1aH+)

 

The higher the pH, the more basic or alkaline is the solution; the lower the pH, the more acidic the solution. The irritation or stinging induced by a product is often directly related to how low the pH is.

Obviously, pH is an important consideration when formulating personal care products. It affects shelf stability, bacterial growth, how well ingredients combine, and how the product interacts with skin or hair. Measurements of pH can be used to reflect the stability of a product. For example, if components in the product hydrolyze, free acid would be released, which would lower the pH of the formulation and provide evidence that ...

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