Buffering

Ingredients with buffering function help to maintain a stable pH level in the cosmetic formula. In the CosIng database, this function is described as the ability to keep the pH of a product at the desired value, even if acidic or alkaline components enter the composition. This is important not only for the "chemical comfort" of the formula, but also for the sensations on the skin: pH affects the condition of the skin barrier, the integrity of the stratum corneum and antimicrobial protection, so too much shift to the alkaline side can increase the risk of irritation. (single-market-economy.ec.europa.eu)

In the finished product, such substances make the product more predictable and gentle to use. They help maintain the stability of texture, color, preservatives and active ingredients, and in skin and hair care reduce the likelihood that the formula will be too aggressive or, conversely, lose effectiveness due to pH fluctuations. This is especially important for cleansers, acid formulas, paints, and products with sensitive assets. (pubmed.ncbi.nlm.nih.gov)

Typical examples of such ingredients are Citric Acid and Sodium Citrate. Citrate compounds are often used in pairs: one part of the system acidifies the formula, while the other helps keep the pH within specified limits. According to Cosmetic Ingredient Review, citric acid and its salts are actually used in cosmetics, including as buffering agents. (cir-safety.org)