Does my product need Microbial Challenge testing?

How do I know if a challengetest is necessary for my product?

Preventing product rotting and mold growth is crucial for product safety and longevity. However, not all products require a challenge test.

First of all, bacteria and fungi need water to live and grow. Waterlesss products are less susceptible to microbial growth. Think of make-up powders or dry shampoo. From a technical standpoint, this is because there is a low amount of water present, which means there are not sufficient water molecules for bacteria or fungi to survive on. Low water activity is also the reason why dried fruit, peanut butter and honey have virtually no spoilage.

Products that are inherently resistant to, often do not need a challenge test. An example is a bar of soap with a very high pH, which kills bacteria and fungi (that's why soap works like soap) or a facial peeling with a very low pH. Other products that do not contain water but are oil-based also do not require a challenge test. Think of a massage oil or an oil for after showering.

Certain ingredients can also act as natural deterrents to prevent the growth of bacteria and fungi. For example, products that have a high alcohol concentration (>20% alcohol) like perfumes, ammonia, or hair dyes containing monoethanolamine can effectively inhibit the growth of microorganisms. Additionally, polar organic solvents such as ethyl acetate and butyl acetate, commonly found in nail polish, have antimicrobial properties. These ingredients create an environment that is unfavorable for the survival and proliferation of bacteria and fungi, ensuring the product remains safe and free from contamination.

In addition to the product and ingredients, the production process and packaging material also influence whether a challenge test is necessary. If a mixture is heated to 65 degrees Celsius for more than 10 minutes during production / filling in the packaging, then almost all bacteria and fungi are killed. This is just like pasteurizing milk, where heating ensures that the milk has a longer shelf life. If a container is used that remains closed, such as a pressurized aerosol can, then there is little chance that bacteria and fungi can enter the aerosol can during use. While a jar of cream that you put your fingers in, has a high chance of contamination.

The step-by-step plan you can use to determine whether a product needs a challenge test:

1. Check the amount of water / water activity of the product
2. Measure the pH of the product
3. Does it contain specific raw materials that provide an anti-microbial environment?
4. What is the production method, and are there any heating steps involved?
5. How well does the packaging protect the product against microbes?

If you are unsure whether your product requires a challenge test, don't worry! SkinConsult is here to assist you in determining if a challenge test is necessary for your product.

We hope to have informed you about challenge tests, what they are and when you are obligated to perform one to have a complete PIF in accordance to EU legislation. Please do not hesitate to contact us if you have any other questions about challenge testing at office@skinconsult.com.

Remember, safety first!