What is the role of pH regulators in formulation?

What is the purpose of a pH regulator in cosmetics?

The measurement of a cosmetic product's pH is a critical step in its formulation. Indeed, to ensure consumer safety, maintain formula stability, and guarantee the effectiveness of the treatments, it is essential that the product's pH is suitable and falls within a well-defined range. To achieve this, formulators use pH regulators. Discover more information about this family of ingredients here.

Published on November 26, 2024, by Pauline, Chemical Engineer — 6 min of reading

What is pH and what is its relationship with the skin?

The pH, or potential of hydrogen, is an indicator of the acidity or alkalinity of a solution or a surface. It is expressed on a scale ranging from 0 to 14 and represents the activity of hydrogen ions H+, which can be compared to their concentration. In an aqueous environment at 25°C, considered a neutral medium, a solution with a pH equal to 7, or between 6.6 and 7.3, is said to be neutral. If its pH is less than 7, it is classified as acidic, and if it is greater than 7, it is said to be basic. In cosmetics, the concept of pH is important because a product that is too acidic or too alkaline can strongly irritate the skin.

The skin's pH is slightly acidic and typically ranges between 4.7 and 5.75.

The natural acidity of the skin is due to the presence on its surface of an acid mantle, the hydrolipidic film. This is a key factor in the homeostasis of the skin barrier, its integrity and its antimicrobial defence capabilities, mainly composed of sebum and sweat. Furthermore, ceramides, essential lipids of the stratum corneum, are synthesised at an acidic pH by pH-dependent enzymes. The dysregulation of skin pH can lead to several discomforts, such as the weakening of the barrier function, destabilisation of the skin microbiota or the appearance of imperfections.

Why is it necessary to use a pH regulator when formulating a skincare product?

In order to respect the physiology of the skin and its natural acidity, cosmetic treatments are generally formulated at pH levels between 4.5 and 7, depending on their type and function. Indeed, serums, lotions and face creams often have a pH close to 4.5, while rinse-off cleansing products can have a pH up to 7. In order for the treatments to adhere to these pH ranges, it is necessary for formulators to use pH regulators, also known as pH adjusters.

The primary function of pH regulators is to adjust the pH of a solution in order to achieve an acid-base balance that respects the skin.

This primary function of pH regulators allows them to fulfil various roles.

Regulators contribute to making cosmetics stable.
pH variations can impact the actives in cosmetic formulas, leading to their degradation, oxidation, or precipitation. pH regulators help stabilise skincare products, ensuring they maintain their properties and effectiveness throughout their lifespan.
pH regulators play a role in the safety of skincare products.
To prevent irritations and other undesirable skin reactions, it is crucial that the pH of topically applied products is compatible with the skin. pH regulators ensure that cosmetics remain within a safe pH range for the skin.
pH regulators enhance the effectiveness of active ingredients.
Some cosmetic ingredients, such as fruit acids (AHA) or vitamin C, are only effective within a specific pH range. Furthermore, certain active ingredients are only compatible with each other at a precise pH, where they can interact without altering their respective properties. The role of pH regulators is therefore to ensure an environment where each active ingredient can fulfil its function, whilst acting in synergy with the others.
pH regulators help to prevent microbial contamination.
The pH plays a significant role in the action of preservatives. Indeed, their effectiveness can be constrained by a pH that is either too high or too low, which can increase the risk of bacterial or fungal proliferation in a product. pH regulators thus help to maintain an environment where preservatives can be fully effective.
pH regulators influence the organoleptic characteristics of skincare.
A pH variation in a skincare product can manifest macroscopically as a change in its texture, viscosity, colour, or smell. By maintaining a constant pH, pH regulators help to preserve the appearance and feel of cosmetics.

The pH regulators that can be found in cosmetic products are predominantly weak acids and bases, meaning they do not fully dissociate in water. Among them, we can mention acetic, adipic, ascorbic, boric, citric, fumaric, glycolic, lactic, malic and uric acids, ammonium, calcium, magnesium, potassium and sodium hydroxides, ammonium, calcium, potassium and sodium phosphates, and alkanolamines, such as ethanolamine, triethanolamine and tromethamine. At Typology, we particularly use citric acid (INCI: Citric Acid), lactic acid (INCI: Lactic Acid), sodium citrate (INCI: Sodium Citrate) and sodium hydroxide (INCI: Sodium Hydroxide) to regulate the pH of our skincare products.