Why is pH important in cosmetics?

pH (potential of hydrogen) is an essential parameter in every cosmetic formulation. It determines not only skin compatibility, but also the stability of the product, the efficacy of the active ingredients, and the microbiological preservation.

A cream with an incorrect pH can:
  • Denature proteins and alter the skin barrier.
  • Inactivate sensitive actives (such as peptides or alpha-hydroxy acids).
  • Cause phase separation or loss of viscosity.

This is why correctly adjusting the pH is one of the most important steps in the final stage of cosmetic development.

The ideal pH range depending on product type

Each type of formulation has an optimal pH range that ensures stability and skin compatibility:
 
Ph range by product type
Product type Recommended pH range
Facial cleansers 4.5 - 6.0
Facial and body creams 5.0 - 6.0
Shampoos and shower gels 4.5 - 6.5
Deodorants 4.0 - 5.0
Chemicals peels (AHA/BHA) 3.0 - 4.0
Haircare products (conditioners) 3.5 - 5.5
Sunscreens 6.0 - 7.5


⇒ You should always verify pH compatibility with the cosmetic actives you are using, since some lose efficacy outside their optimal range.

When should the pH be adjusted in a cosmetic formula?


The pH adjustment must be carried out at the end of the formulation process, once the emulsion is complete and at room temperature.
This allows you to measure a stable value and avoid false readings.

Key tips:
  • Always measure pH with a calibrated pH meter, not with indicator strips (they are only approximate).
  • Adjust slowly, drop by drop, with gentle stirring to avoid breaking the emulsion.
  • Wait a few minutes before measuring again: the value may change after homogenization.

Most commonly used pH adjusters in cosmetics

Depending on whether you need to increase or decrease the pH, different agents are used:

↓ To lower pH (acidify):

  • Lactic acid → Mild, biodegradable, and widely used in facial cosmetics.
  • Citric acid → Cost-effective but may crystallize if used in excess.
  • Acetic acid → Less common due to its odor, but effective in small amounts.

↑ To raise pH (alkalinize):

  • Sodium hydroxide (NaOH) → Strong; recommended in diluted solutions.
  • Triethanolamine (TEA) → Traditionally used in O/W emulsions, though increasingly restricted in certain regions.
  • Arginine → A natural alternative with good skin compatibility.

In natural or sustainable cosmetics, lactic acid and arginine are especially valued due to their biotechnological origin and excellent dermal compatibility.

Interactions with actives and formula stability

pH directly influences the stability of cosmetic actives:
  • Vitamins (C, B3) → require specific pH values to remain active.
  • Organic acid preservatives (sorbate, benzoate) are only effective at pH < 5.5.
  • Thickening polymers (such as carbomers) require neutralization to achieve maximum viscosity.

Therefore, pH adjustment should not be treated as a routine step but rather as a strategic part of formulation.

Common mistakes when adjusting pH

  1. Adjusting while the formula is still hot → pH changes with temperature.
  2. Adding adjusters undiluted → can break the emulsion or precipitate actives.
  3. Not recalibrating the pH meter → leads to inaccurate readings that compromise the batch.
  4. Forgetting to re-measure pH after 24 hours → some formulas shift slightly after resting.

Conclusion


A well-adjusted pH ensures a safe, effective, and stable formula.
It is a simple parameter to measure, but it has a major technical and sensorial impact on the final product.

For over a century, LEMMEL has been supplying cosmetic raw materials —including lactic acid and derivatives that help regulate pH— to support formulators in achieving excellence in their developments.

► Discover more about our cosmetic formulation solutions at lemmel.net