Anhydrous formulations contain no intentionally added water and are generally based on oils, esters, waxes, butters, silicones or other non-aqueous materials.

Examples include lip balms, lipsticks, facial oils, cleansing oils, body balms, petroleum-based products and certain solid sticks.

The absence of water can provide formulation advantages. Ingredients that are unstable in aqueous environments may be easier to formulate in anhydrous systems, and many microorganisms require available water for growth.

However, anhydrous does not mean automatically microbiologically safe. Water can be introduced during consumer use, particularly in products used with wet hands or in the shower.

Stability

Oxidative stability is often an important concern. Oils rich in unsaturated fatty acids can oxidize during storage, producing changes in odor, color and potentially the sensory characteristics of the product.

Antioxidants, oxygen-limiting packaging and appropriate storage conditions may therefore be important.

Texture

In balms and sticks, wax selection and crystallization behavior strongly influence hardness, payoff, melting point and sensory characteristics.

Cooling rate can affect crystal formation and therefore the final texture of the product.

References

Barel, A. O., Paye, M. and Maibach, H. I. Handbook of Cosmetic Science and Technology. CRC Press.

European Commission. CosIng – Cosmetic Ingredients Database.

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