Sorbic Acid
Also known as 2,4-Hexadienoic acid, Hexa-2,4-dienoic acid, (2E,4E)-hexa-2,4-dienoic acid, E200
“EU CosIng says: restricted.”
Sorbic acid is a polyunsaturated organic acid preservative (E200) approved by CIR (1988, confirmed 2006) as safe in current cosmetic practice and listed in EU Annex V (Reference 4) at a maximum of 0.6% calculated as the free acid. Walker (1990) reviewed extensive toxicological data showing very low mammalian toxicity, no carcinogenicity, and metabolism via fatty-acid pathways, while noting rare idiosyncratic non-immunological contact urticaria and pseudo-allergy. Dendooven et al. (2021) report that allergic contact dermatitis from sorbic acid and potassium sorbate is uncommon but likely underestimated, with patch-test sensitization rates historically reported around 0–0.8% in repeat-insult patch tests.
Effective against yeasts and molds; useful adjunct preservative at acidic pH (active form: undissociated sorbic acid).
Long history of safe use in cosmetics and as food additive E200; metabolized like other dietary fatty acids.
Practically nontoxic in acute and subchronic mammalian studies; no evidence of carcinogenicity, mutagenicity, or teratogenicity at relevant exposures (Walker 1990; CIR 1988).
Approved at the same EU Annex V cap as its salts, allowing formulators to choose acid vs. salt form based on solubility and pH without changing the regulatory ceiling.
- · Allergic contact dermatitis — uncommon but documented (sensitization rates ~0–0.8% in repeat-insult patch tests; Dendooven 2021 notes likely underestimation; cross-reactivity with potassium sorbate).
- · pH-dependent activity — antimicrobial efficacy drops sharply above pH ~6.5 (pKa 4.76), so finished products with higher pH may be under-preserved despite the ingredient being present.
Non-immunological contact urticaria — transient stinging or wheal reaction, particularly perioral; mechanism is non-IgE-mediated histamine release rather than true allergy (Walker 1990; PMID 7067435).
Oxidative discoloration — sorbic acid is prone to atmospheric oxidation, which can cause yellowing of the finished product; chelators or co-formulation with citric acid are commonly used to manage this.
CIR Quick Reference Table (12/2017, revised 07/2018) — SORBIC ACID row: Finding=S, Citation=JACT 7(6):837-80, 1988 confirmed 04/06
“Sorbic Acid”— QRT-122017revised072018.pdf, p. 124
EU Cosmetics Regulation (EC) No 1223/2009, Annex V (preservatives), Reference 4 — Hexa-2,4-dienoic acid and its salts (Sorbic acid, calci…
“Hexa-2,4-dienoic acid and its salts”— EU Reg 1223/2009 Annex V, Reference 4 (current consolidated)