Benzoic Acid

Evidence by route

About this ingredient

Benzoic Acid is an aromatic acid, a natural component of several resins (benzoin gum, Peruvian balsam) and cranberries. Used in cosmetics, pharmaceuticals, and food as a preservative – more often as its sodium salt (Sodium Benzoate, E211). Mechanism. Active in acidic medium (pH below 5.5): in its undissociated form it crosses bacterial and fungal cell walls and acidifies the cytoplasm, inhibiting anaerobic metabolism. Particularly effective against yeasts and moulds; weaker against gram-negative bacteria. Where applied. Toners, shampoos, shower gels, face gels, prescription ointments, foods (E210 and E211). Cosmetic concentration up to 2.5% (Sodium Benzoate up to 2.5% per EU Cosmetics Regulation Annex V). In Spanish pharmacy lines it appears in ISDIN, Avène Trixera, Bioderma Sensibio. Safety. CIR and SCCS confirm safety at cosmetic concentrations. Skin irritation may occur in some patients at over 0.5% – usually mild and reversible. Allergic contact dermatitis reports are isolated; pseudo-allergic, non-immune mediated reactions (oedema, erythema) are more common. Combined with vitamin C in a formula and under UV, sodium benzoate can form trace benzene, so formulators avoid that combination or add EDTA and skip 'high vitamin C' label claims. Pregnancy and lactation – safe. AEMPS and FDA do not restrict food or topical use at normal doses. Functional role. An adjunct preservative, not a cosmetic active. No standalone skin benefit.

Tolerability and safety

Skin types

Frequently asked questions