What is it?
Water is the main ingredient in many lotions, creams, shampoos, body washes, cleansers and toners. It dissolves other ingredients, helps them spread and forms the watery part of creamy emulsions. On ingredient lists it appears as “water,” as “aqua,” the name used in the European Union, or as “water/eau” in Canada; all of these mean the same ingredient. The water that goes into cosmetics is purified rather than taken straight from the tap.
Key information
- Water, aqua and eau are different label names for the same ingredient.
- Ingredients above 1 percent are listed from most to least by weight, so when water comes first it is the largest single ingredient.
- Cosmetic makers purify their water, for example by deionization combined with filtration, ozone or ultraviolet light.
- The FDA advises against adding water to products such as mascara, because it can bring in microbes and dilute the preservatives.
More information
Cosmetic manufacturers purify the water they use as an ingredient, for example with deionization, which removes dissolved mineral salts, combined with fine filtration, ozone or ultraviolet light to control microbes. Quality matters because products that contain water give microbes a favorable place to grow. A 2026 study from a cosmetics plant notes that water systems are an important source of contamination and that microorganisms can survive even advanced purification, and the FDA lists contaminated water among the possible causes of microbial contamination in cosmetics.
Water usually heads the label because of how labels are ordered. U.S. rules require cosmetic ingredients to be listed in descending order of predominance, although those present at 1 percent or less may follow in any order, and Canada’s rules are similar. So when water comes first, it is the largest single ingredient by weight. Products made without water, such as oils, balms and many powders, start with something else.
Water is not a safety concern in its own right; the questions are purity and preservation. Because water supports microbial growth, water-based products rely on preservatives. The FDA advises consumers not to add water or saliva to products such as mascara, because doing so can introduce harmful microorganisms and water down the preservatives that keep them from growing.
Label tip: “water,” “aqua” and “eau” are the same ingredient, and Canadian labels may show “aqua” alone or “water/eau.” After water, the other ingredients are listed from most to least until you reach those at 1 percent or less.
Sources: FDA: Cosmetics Labeling Guide; Health Canada: Industry guide for the labelling of cosmetics; FDA: Microbiological safety and cosmetics; Applied Microbiology and Biotechnology (2026): Disinfectants against Pseudomonas aeruginosa from cosmetic manufacturing environments
