Is there such a thing as preservative-free?
In the skincare world, preservatives are essential ingredients that help prevent the growth of harmful microorganisms such as bacteria, fungi, and viruses in cosmetic products. Preservative systems ensure that these products remain safe and effective, which is why all skincare products must have an effective preservation system and be thoroughly tested through microbial challenge testing. If all products must have preservation systems, why does C.R.E.A.M. 2.0 not have any preservatives? The short answer is that while it has no traditional preservatives, it still has a robust preservation system through hurdle technology. This article will discuss hurdle technology and how we achieved that in C.R.E.A.M. 2.0.
What is Hurdle Technology?
Hurdle technology is a preservation technique that uses multiple factors to create a barrier against the growth of microorganisms in products. This technique combines different preservation methods, such as pH adjustment, chelating agents, and antimicrobial ingredients, to create a synergistic effect that inhibits microbial growth. The goal of hurdle technology is to make it difficult for microorganisms to survive by simultaneously targeting multiple aspects of their survival mechanism.
Hurdle technology has been used in the food industry for many years and has recently gained popularity in the skincare industry due to its effectiveness and safety. By using hurdle technology, it is possible to create self-preserving skincare creams that do not require traditional preservatives.
Components of Hurdle Technology
pH Adjustment
pH adjustment is a crucial aspect of hurdle technology in skincare formulation. Most microorganisms thrive in a neutral pH environment, so lowering a product’s pH can help inhibit microbial growth. The ideal pH range for skincare products is between 4.5 and 5.0, which is slightly acidic and helps promote skin barrier formation. By adjusting the pH of a product, it becomes a less hospitable environment for bacteria, fungi, and other microorganisms.
C.R.E.A.M. 2.0 is buffered to a pH of 4.75 which is an ideal pH to end a routine and, at the same time, makes it harder for most microbes to grow and multiply.
Water Activity
Water activity refers to the amount of available water in a product that is free to support microbial growth. A lower water activity means that there is less available water for microorganisms to grow in. This can be achieved by using ingredients that are hygroscopic, meaning they absorb water and reduce the water activity of the product. By reducing the water activity of a product, it becomes more difficult for microorganisms to survive and multiply.
Glycerin is an awesome ingredient for the skin, but its other secret benefit is reducing water activity in formulations. At 8% on its own, it can reduce water activity from 1 to 0.97, which is enough to inhibit the growth of Pseudomonas aeruginosa. Panthenol is another humectant capable of decreasing water activity aside from its benefits for the barrier. Essentially, we lowered the water activity in C.R.E.A.M. 2.0 to a point where it is hard for various microbes to grow.
Chelation
Chelating agents are ingredients that are added to skincare products to bind with metal ions, which are needed for microbial growth. When metal ions are present, they can act as a food source for microorganisms, allowing them to grow and multiply more rapidly. By binding to these metal ions, chelating agents prevent microbial growth and help to preserve the product. Common chelating agents used in skincare products include disodium EDTA, sodium phytate, and citric acid. We previously used disodium EDTA in C.R.E.A.M. 1.0, but we decided to switch to a more biodegradable chelating agent: Tetrasodium Glutamate Diacetate
Good Manufacturing Practices
Good manufacturing practices (GMPs) are essential for ensuring the safety and efficacy of skincare products. GMPs include strict guidelines for product formulation, manufacturing, packaging, and storage to prevent contamination and ensure consistent product quality. Following GMPs is crucial for creating a self-preserving skincare product that is safe for use. We manufacture our products in a secure space where GMP is strictly followed.
Anti-Microbials
In addition to using hurdle technology factors such as pH, water activity, and chelating agents, antimicrobial ingredients can be added to skincare products to further inhibit the growth of microorganisms. Antimicrobial ingredients commonly used in skincare products include phenoxyethanol, sodium benzoate, and potassium sorbate. Some ingredients that are used as actives in skincare also have some antimicrobial properties. One example is Bisabolol, which is used as a soothing agent but also has some antibacterial properties. 
Initially, we were going to use a super mild blend used in “no-tears” baby products: Benzyl Alcohol (and) Benzoic Acid (and) Dehydroacetic Acid (and) Tocopherol but we ended up not needing it.
Testing
We sent out multiple formulations with varying concentrations of preservatives. Our goal was to determine the minimum concentration needed for C.R.E.A.M. 2.0, so they must be tested using USP51 Antimicrobial Effectiveness Testing. Essentially, in this test, they purposely add certain concentrations of bacteria, yeast and mold and test if the formulation can decrease the number (1 logarithmic reduction). Since implementing Hurdle technology, we hope to use the least concentration of preservatives as much as possible. At the back of our minds, we are still hoping that the hurdle technology works on its own and not have to use preservatives, since we were able to pull it off with Wave 2.0. Luckily, the results of the USP51 came back, and all of the formulations passed, even the one without any preservatives. 
In conclusion, hurdle technology is a multifaceted approach to preserving skincare products that involves using pH adjustment, water activity reduction, chelation, good manufacturing practices, and antimicrobial ingredients. Essentially, we tweaked small things that can contribute to the preservation system. Then by combining these small factors, we could formulate a stable C.R.E.A.M. 2.0 without adding any additional preservatives.