“Microbiome-friendly” means a product does not disturb the microbial balance of the skin (or other relevant body parts such as the gut or mouth), and helps preserve the diversity of the natural microbiome.
For more context, our skin microbiome refers to the trillions of microscopic organisms, mostly bacteria, that live on and in our skin's various layers. A healthy or “balanced” skin microbiome is like a diverse rainforest—the more strains which coexist, the healthier the skin.
When your skin microbiome is off balance, meaning that the healthy balance of good bacteria on your skin is not intact, this can compromise your skin’s natural barrier. This leads to inflammation which can show up in the skin as dehydration, accelerated aging, sensitive skin, or even flares of chronic skin conditions such as acne, eczema, rosacea, and psoriasis.
This can be a vague and tricky term because there’s not a standardized definition. This means, someone can say “microbiome-friendly” and can do any of the following: no testing whatsoever, in vitro testing (outside of humans, in a petri dish), or in vivo testing (testing done on humans). Some also claim “microbiome-friendly'' based on one individual ingredient that might have a positive impact on the microbiome (per ingredient supplier data), but the final formulation can include, for example, three other ingredients that all disrupt the skin microbiome. So, take this term with a grain of salt.
When Dr. Whitney Bowe Beauty says a product is “microbiome-friendly”...
It means we have conducted in vivo, human studies using next-generation sequencing technology. This is what we believe to be the most advanced form of microbiome testing available today, aka the “gold standard” of microbiome testing.