What it is
Sorbic acid is an unsaturated carboxylic acid widely used as a preservative against molds and yeasts and, to a lesser degree, bacteria. It is most effective in acidic formulas, where the undissociated acid form predominates, and is often paired with other preservatives for broad coverage. In sunscreens it helps protect the product from microbial spoilage over its shelf life.
Safety & warnings
Generally well tolerated and non-comedogenic, but sorbic acid can cause mild, non-allergic irritation or a transient stinging or flushing sensation in some people, particularly on sensitive or broken skin. Contact allergy is uncommon.
Origin & sourcing
First isolated from the berries of the rowan (mountain ash); the cosmetic grade is produced synthetically.
History
It was originally derived from rowan berries and later adopted broadly as a food and cosmetic preservative once economical synthesis was developed.
Questions everyone asks
What does sorbic acid do in sunscreen?
It is a preservative that inhibits mold and yeast, helping keep the product safe to use through its shelf life.
Does sorbic acid work at any pH?
It is most effective in acidic formulas, which is why it is often combined with other preservatives for fuller coverage.