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6 Final Report on the Safety Assessment of Sodium Borate and Boric Acid

Sodium Borate and Boric Acid are used in cosmetics as preservatives, antiseptics, water softeners, pH adjusters, emulsifiers, neutralizes, stabilizers, buffers, or viscosifiers.

Investigators have reported that Sodium Borate and Boric Acid are poorly absorbed through intact skin; however, both compounds are absorbed through abraded, denuded, or burned skin. In a 90-day dermal toxicity study, Boric Acid (25-200 mg/kg/day) was nonirritating and nontoxic when applied to the intact skin of rabbits. Sodium Borate and Boric Acid were relatively nontoxic when tested orally in animals.

A 5% Sodium Borate in water solution was mildly or moderately irritating to the skin of rabbits and guinea pigs, and practically nonirritating when instilled in rabbits' eyes. Acute studies indicated that, at 10% in water, Boric Acid was mildly or moderately irritating to the skin of rabbits and guinea pigs.

Sodium Borate or Boric Acid in the diet of rabbits and rats caused growth retardation. Doses of up to 1.06 g/kg/day Sodium Borate in the diet of male rats exerted toxic effects on the gonads as well as infertility.

Boric Acid was nonmutagenic in the Ames test. Boric Acid induced reduced eye phenocopies and lumpy chromosomal inclusions in Drosophila melano-gaster. Limited carcinogenic and teratogenic studies did not indicate a statistically significant effect.

In clinical studies, cosmetic formulations containing up to 3.2% Sodium Borate were nonirritating to moderately irritating and nonsensitizing when applied to human skin. Formulations containing up to 2.4% Boric Acid were moderately irritating and practically nonirritating. Photopatch testing of formulations containing 1.1% or 1.7% Sodium Borate were negative.

Based on the increased absorption of Boric Acid by damaged skin as compared to intact skin, as well as the testicular atrophy observed in experimental animals, the Panel concluded that Sodium Borate and Boric Acid, in concentrations ≤ 5%, are safe as cosmetic ingredients when used as currently recommended; however, cosmetic formulations containing free Sodium Borate or Boric Acid at this concentration should not be used on infant or injured skin.