Sorbic Acid

Sorbic Acid is a preservative that stops your product from spoiling by stopping microbes from growing.

As a preservative, it's kind of a specialist: it has a broad spectrum of activity against yeast and molds but is weaker against bacteria. That's why it's often paired with another preservative to cover that gap.

This ingredient is also pretty picky about pH; it performs best at pH 6.5 or below.

At the right pH level, sorbic acid is "active" and can slip through the outer wall of a microbe. Once inside, it turns the cell's interior more acidic to shut down the microbe from the inside.

The EU caps this ingredient at 0.6% while the CIR has concluded it's safe at concentrations up to 1%. It's most often used around 0.05-0.2% in cosmetics.

Though this ingredient is considered low-sensitizing and well-tolerated, a very small number of people may have a contact allergy to it. Be sure to patch test if you have a history of allergies towards preservatives.