First treatment essences are products that typically contain some form of yeast (or other) ferment, and they are meant to be applied prior to any toners or other essences. They are usually known for their ability to reduce redness and improve skin health and function. As a rosacea sufferer, anything that can possibly reduce redness is going to be an attractive option.
My first product in this category was the Nature Republic Saccharomyces The First Treatment Essence. I really enjoyed that product, but it was unfortunately discontinued and I was put on a mission to find a replacement. The COSRX Whitening Power Essence has been my first attempt.
As many a skincare nerd will know, there are some types of products in which the pH is hugely important to the product’s purpose and effectiveness. BHAs, AHAs, or L-ascorbic acid serums are ‘pH dependent’, which means their effectiveness is altered by the pH of the product formulation, or by the pH of the skin they are applied to.
These products tend to perform better at a pH that is lower than the natural pH of your skin. Your skin’s pH hangs around 4.5-5.5, and the ideal pH for these products, such as Vitamin C, can be as low as 2.5. What ends up happening is that some of the effectiveness of these products is used up in the effort it takes to lower the pH of your skin to a suitable range. One way to resolve this is to use a pH-adjusting toner to do the grunt work of lowering the skin’s pH so that the pH dependent products can be more effective at what they do. This is the role of a product like the COSRX BHA/AHA Clarifying Treatment Toner.