Unlocking the Power of Water Activity in Cosmetics

If someone were to ask you what blush, eyeliner and lotion all had in common, chances are your first answer wouldn’t be water. 

But water—specifically water activity —plays an incredibly important role in the formulation and preservation of every cosmetic. From preventing clumping to inhibiting microbial growth and ensuring production consistency, water activity is a silent hero in the cosmetic industry.

Just like many foods and pharmaceuticals, the largest component of many cosmetic products is water.  But how that water is measured can greatly impact companies’ abilities to maintain desired quality characteristics, hit shelf-life goals, and choose the correct types of packaging. 

Water activity, denoted as a_w, plays a pivotal role in the formulation and preservation of cosmetics. This measure can be used to evaluate the availability of water within a product, influencing its stability, shelf life, and overall quality. Cosmetics manufacturers must carefully monitor water activity as it directly impacts microbial growth, chemical reactions, and the deterioration of product quality.

Cosmetic companies that measure water activity understand that it is a critical parameter towards preserving the products they work so hard to make.  Whether it is preventing caking/clumping of powders, avoiding unwanted mold and microbial growth, or simply making a consistent product, the precision offered by primary water activity methods ensures the cosmetics live up to their brand’s reputation.  This is especially true for products having a water activity less than 0.75 aw, such as blushes, lipsticks, lip balms, color palettes, face/foot powders, bronzers, and deodorants.

Water Activity’s Role in Regulatory Compliance

Water activity is already widely used in the food industry, and its use is critical in the pharma industry with the passing of USP <922>, which moved water activity from a guidance metric to a requirement.  

ISO 29621 Cosmetics references water activity and offers guidance to cosmetic manufacturers to help define products having microbiological risks. 

Recently, the FDA expanded its authority with the passing of the Modernization of Cosmetics Regulation Act of 2022 (MoCRA). As the majority of MoCRA's provisions are set to take effect at the close of 2023, it is crucial for all cosmetics companies to familiarize themselves with the upcoming regulatory requirements and proactively take the necessary steps now to position themselves favorably for the challenges ahead.

Water Activity Monitoring in Cosmetics: Bridging the Gap

As regulations evolve, companies must validate their products before sale, ensuring they meet safety standards and remain stable throughout their lifecycle. Effective tracking of water activity aids in monitoring product quality as it moves through the distribution chain. Water activity measurements can be added as part of Good Manufacturing Practices (GMP) and as Hazard Analysis Critical Control Points (HACCP) to identify and manage safety risks.

Proactive measures, such as adjusting formulations and implementing robust quality control practices, will empower manufacturers to navigate the evolving landscape of cosmetic regulations and maintain the integrity of their products.

Water activity serves as a crucial parameter in the formulation of cosmetics, offering valuable insights to manufacturers striving for product stability and quality. By understanding the water activity, formulators can precisely control the moisture content in cosmetic formulations. This precision is essential in achieving the desired texture and compressibility, consistency, and shelf life of products. Formulators can tailor formulations to strike a balance, harnessing the moisturizing benefits of water without compromising the product's integrity. Additionally, knowledge of water activity assists in preventing issues like separation, discoloration, or changes in fragrance, contributing to the overall sensory experience for consumers. Water activity is also the force that controls moisture migration, not moisture content. Thus, incorporating water activity considerations into cosmetic formulations is a strategic approach that enhances the quality, safety, and longevity of cosmetic products.

The Impact of Water Activity on the Stability of Cosmetic Formulations

Processes involving water are influenced by water activity, not moisture content. This encompasses phenomena such as moisture migration, chemical degradation, enzymatic and browning reactions, oxidation, and of course, microbial growth.

The driving force of moisture migration are differences in water activity between components or between a component and environmental humidity. Knowledge of whether water will adsorb or desorb from a particular component is essential to prevent degradation, especially if the substance is moisture sensitive. Driven by physics, water will move from a higher water activity to a lower one until equilibration is achieved. Matching the water activities of the components will ensure that moisture stays put.


Water can influence chemical and enzymatic reactivity in many ways. It may act as a solvent, a reactant, or change the mobility of the reactants by affecting the viscosity of the system. Typically, as the water activity level is lowered, the rate of chemical degradative reactions decreases, with the exception of oxidation. At low water activities, ingredients that are susceptible to oxidation are at a higher risk. 


Water activity is also an important factor affecting the stability of powders and dehydrated products during manufacturing and storage. Controlling water activity in a powder product maintains proper product structure, texture, stability, density, and rehydration properties.  Knowledge of the water activity of powders as a function of moisture content and temperature is essential during processing, handling, packaging, and storage to prevent the deleterious phenomenon of caking, clumping, collapse, and stickiness,

Embrace Water Activity: Safeguard Your Brand, Delight Your Consumers!

 
Water activity, often overlooked, is a silent guardian in cosmetics. It's the key to preventing clumping, inhibiting microbes, and ensuring consistency. For cosmetics manufacturers, measuring water activity is not just about quality; it's about protecting consumers and delivering a consistent brand experience.

 
Why Water Activity Matters:


1. **Quality Assurance:** Precision in water activity measurement prevents issues like caking and unwanted growth, ensuring your products live up to your brand's reputation.

2. **Regulatory Compliance:** Stay ahead of evolving regulations, such as the Modernization of Cosmetics Regulation Act of 2022 (MoCRA), by proactively incorporating water activity monitoring into your processes.

3. **Consumer Satisfaction:** Water activity influences texture, consistency, and longevity. By mastering it, you enhance the overall sensory experience for your consumers.

4. **Brand Integrity:** Consistency in formulation, guided by water activity, is your strategic approach to maintaining the quality, safety, and longevity of your cosmetic products.
 

Take Action Now:

1. **Invest in Precision:** Utilize primary water activity methods for accurate measurement. 

2. **Stay Informed:** Keep abreast of regulatory changes to position your brand favorably.

3. **Proactive Formulation:** Adjust formulations based on water activity insights to ensure a consistent and delightful consumer experience.

By prioritizing water activity measurement, you're not just safeguarding your brand; you're offering a promise of reliability and quality to your consumers. Act now, and let water activity be your guide to a thriving and trusted cosmetic brand.