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.