Phages vs. Probiotics: Exploring Quality

Phages vs. Probiotics: Exploring Quality

One of the most challenging, and often frustrating, aspects of navigating the modern skincare world is making sense of the dizzying array of formulations and ingredients, many of which have complicated and unfamiliar names. The advent of microbiome-focused skincare has only added to this challenge, introducing consumers to ingredients such as Lactobacillus ferment and Lactococcus ferment lysate and terms like prebiotic, probiotic and postbiotic, which can be confusing for even the savviest skincare user. No wonder it sometimes feels like you need a degree in biology to make sense of it all!

At Ellis Day Skin Science, we want to help our users better understand the ingredients in our breakthrough product Wild Resilience™ Active Phage Serum and why it is unlike anything else on the market today, including those labeled as probiotics.

The term “probiotic” generally refers to living microbes - usually bacteria or yeast - that are believed to have health-promoting qualities. These are typically either ingested or applied topically in order to replenish or supplement the native microbiome. Importantly, the key word here is living. In order to be a true probiotic, a product should contain organisms that are, in fact, alive. 

In contrast, the active ingredient in Wild Resilience™, our proprietary Cutiphage™, is not a probiotic, and it promotes skin health in a completely different way. Cutiphage™ is composed of tiny microbes known as bacteriophages (or phages) that target and kill blemish-causing strains of a skin bacterium known as Cutibacterium acnes (C. acnes for short). Unlike bacterial or yeast cells, these phages are not “alive” in the true sense of the word; that is, they only become active when they come into contact with their target bacteria. Unlike bacteria, which eat, breath, and reproduce on their own, phages alone are inert and can only make more of themselves inside a host bacterial cell. While both are small and invisible to the naked eye, phages are also a lot tinier than bacterial cells, with most ranging in size from 0.024 to 0.2 micrometers in length. In contrast, most bacterial cells are between ~0.5 and 5 micrometers.

All of these properties combine to make the use of phages, particularly those that target and kill blemish-causing bacteria, an ideal strategy for improving skin health. However, as with any skincare ingredients, quality and activity are of utmost importance. For phages, that means a few things. For example, it’s critical that a product contains the right type of phages to target the problem bacteria. Most phages are highly specific to one type of bacteria, so the wrong phages will, at best, have no effect and, at worst, kill beneficial bacteria in your microbiome. Another key issue is phage potency: the phages need to be at a high enough concentration to maintain their activity and stability and to actually have an effect once applied. At Ellis Day Skin Science, we use a high concentration of phage in Wild Resilience™  (there are 300 billion phages in every bottle!) to ensure maximum potency and blemish-fighting activity. Lastly, our expert team of scientists has developed a serum formulation that maintains phage stability and activity even at room temperature. So unlike probiotic products, you don’t have to worry about keeping Wild Resilience™ in the fridge… although you can if you want to (you shouldn’t put it in the freezer, though)!

Skincare science has advanced by leaps and bounds over the past decade, and it can be difficult to keep up with all of the new products and active ingredients on the market. At Ellis Day Skin Science, we want to empower our customers by helping to decode the science behind what makes Wild Resilience™  and our proprietary Cutiphage™ so powerful and unique. It truly is an exciting time to be leading the way in developing phage-based skincare and making this revolutionary technology available to all. 

As always, if you have any specific questions about the science behind Wild Resilience and phage-based skincare, please email us at We’re happy to help!



  1. Frerejacques M, Rousselle C, Gauthier L, et al. Human Skin Bacterial Community Response to Probiotic (Lactobacillus reuteri DSM 17938) Introduction. Microorganisms. 2020;8(8):E1223. Published 2020 Aug 11. 
  2. Draelos ZD. The Role of ‘Biotics’ in Skincare. Dermatology Times. 2020;41(5):11.


About Ellis Day Skin Science

We believe that modern skincare must be grounded in true microbiome science. We believe the answers are in the wild, natural world, which includes the surface of your skin. 

At Ellis Day Skin Science, we pioneer natural phage-based products that target and kill bad bacteria associated with inflammation, damage, and aging, and enable good bacteria to flourish. By doing so, we aim to reset your microbiome for optimal skin health.

We use cutting-edge science to leverage nature, creating products that are just as kind and conscientious as they are effective, so that all can feel empowered with balanced, clear, radiant, and resilient skin.

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