Table 3. Typical water activities of various personal care products2

Measuring water activity is especially useful for formulations that are atypical, such as: w/o emulsions, low-water content products, anhydrous products such as lipsticks and powders, and water extracts where the addition of high levels of glycols, even as extracting solvents, can be used to lower the water activity below 0.7 to avoid the need for additional preservatives.