When you see “water\aqua\eau” on a product’s ingredient label, it simply means water. Manufacturers of cosmetics and personal care products are required by law to list all of the ingredients in the formula using their INCI (International Nomenclature of Cosmetic Ingredients) names. The INCI name for “water” is “aqua”. The term “eau” is French for water. If a cosmetics company puts water\aqua on their packaging in Canada, by law they have to add the French (no English without French), resulting in “water\aqua\eau”.
Types of water used in cosmetic formulations
Water is used in virtually every type of cosmetic and personal care product. It must be free of toxins, pollutants, and microbes. There are several types of purified water that can be used, including distilled, deionized, and demineralized water.
Distilled water is the oldest form of purifying water. It involves boiling water in a still. Then, the vapor is collected in a condenser and cooled to reform the water. In theory, this process should remove all traces of contaminants except for those that boil at a temperature lower than water, such as some alcohols.
Deionized water is water that has had almost all of its mineral ions removed, including sodium, calcium, iron, copper, chloride, and sulfate. Deionization is a chemical process that uses specially manufactured ion-exchange resins, which exchange hydrogen and hydroxide ions for dissolved minerals, and then recombine to form water.
Demineralization is often a term used interchangeably with deionization. Similar to deionized water, demineralization removes all minerals found in tap water. This process is usually done when the water will be used for chemical processes and the minerals present may interfere with the other chemicals. With the demineralization process, the water is “softened” by replacing the undesired minerals with different salts (i.e NaCl).
In cosmetics and personal care products, water is primarily used as a solvent to dissolve other ingredients. Additionally, water is used along with various types of oils to form emulsions. These can either be oil-in-water or water-in-oil emulsions, depending on the ratios of the oil phase and water phase.
The quality of water used in the production of cosmetics and personal care products is monitored according to Good Manufacturing Practices outlined in FDA’s Guidance on Cosmetic Manufacturing Practice Guidelines, and in international guidelines on Good Manufacturing Practices known as ISO 22716.
References: Quora, “Why do cosmetics companies call water “aqua”?”, Chemist Corner, “Different Water Used in Cosmetic Formulating” , Wikipedia, “Purified Water”, Cosmetics Info, “Water”.