The Ordinary Glycolic Acid 7% Exfoliating Toner 100ml

Glycolic Acid 7% Exfoliating Toner (previously Glycolic Acid 7% Toning Solution) is an exfoliator that significantly soothes skin texture and promotes the appearance of a more even skin tone, as well as more luminous skin, with regular use. It also reduces the appearance of lines and wrinkles. The water-based toner format is suited to daily use.
It contains a 7% concentration of Glycolic acid - a well-studied alpha-hydroxy acid - and a plant-derived Tasmanian Pepperberry derivative, which varies in colour seasonally, and which may cause an apparent colour variation in the formula from time to time.
This formula should not be used on sensitive, peeling or compromised skin. 
The pH of this formula is approximately 3.6. Glycolic Acid has a pKa of 3.6 and pKa is the most important aspect to consider in formulating with acids. pKa describes the acidity of a molecule. When pKa is close to pH, there is an ideal balance between salt and acidity, maximizing effectiveness of the acid and reducing irritation.