Sodium Hydroxide

What Is It?

Sodium Hydroxide, Calcium Hydroxide, Magnesium Hydroxide and Potassium Hydroxide are white solids which occur in several forms, including powders. In cosmetics and personal care products, Sodium, Calcium, Magnesium and Potassium Hydroxide are used in the formulation of bath products, cleansing products, fragrances, foot powders, hair dyes and colors, makeup, nail products, personal cleanliness products, shampoos, shaving products, depilatories, skin care products, and suntan products. Sodium and Calcium Hydroxide are also used in hair straighteners and hair wave sets.

Why is it used in cosmetics and personal care products?

Sodium Hydroxide, Calcium Hydroxide, Magnesium Hydroxide and Potassium Hydroxide are used to control the pH of cosmetics and personal care products. Magnesium Hydroxide is also used as an absorbant.

Scientific Facts:

Sodium Hydroxide has historically been used to hydrolyze fats and form soaps. It is also called caustic soda, soda lye or sodium hydrate. Calcium Hydroxide is also know as hydrated lime. The mineral form of Calcium Hydroxide is called portlandite. Magnesium Hydroxide is also know as milk of magnesia. The mineral form of Magnesium Hydroxide is called brucite. Potassium Hydroxide is also known as potash lye or caustic potash. Potassium Hydroxide has the ability to attract water molecules from the surrounding environment and eventually dissolves in the water it absorbs.

Safety Information:

The Food and Drug Administration (FDA) includes Sodium Hydroxide, Magnesium Hydroxide and Potassium Hydroxide on its list of substances affirmed as Generally Recognized as Safe (GRAS) for direct addition to food. All three ingredients, as well as Calcium Hydroxide are also approved as indirect food additives for use as defoaming agents in the manufacture of paper and paperboard used as food packaging. Sodium and Potassium Hydroxide can be used for the production of cacao products. The FDA has approved Magnesium Hydroxide for use in Over-the-Counter (OTC) antacid drug products.

More safety Information:

Concentrated Sodium Hydroxide, Calcium Hydroxide, Magnesium Hydroxide and Potassium Hydroxide are strong irritants and corrosive to the skin, eyes, respiratory tract and gastrointestinal system if ingested. The severity of effects caused by Sodium, Magnesium and Potassium Hydroxide is a function of the concentration, the pH, the length of tissue contact time, and local conditions and skin type.

The Joint FAO/WHO Expert Committee on Food Additives has not limited the Acceptable Daily Intake of Sodium Hydroxide, Magnesium Hydroxide or Potassium Hydroxide.

FDA Code of Federal Regulations for

Sodium Hydroxide

Magnesium Hydroxide

Potassium Hydroxide

Potassium and Sodium Hydroxide

Sodium, Calcium, Magnesium and Potassium Hydroxide 

Sodium Hydroxide and Potassium Hydroxide are listed in the Cosmetics Directive of the European Union (see Annex III) and may be used at the following concentrations and pH values: 5% by weight in nail cuticle solvents, 2% by weight in hair straighteners for general use, 4.5% by weight in hair straighteners for professional use, up to a pH 12.7 in depilatories, and up to pH 11 in other uses as a pH adjuster. The nail cuticle solvents and the general use hair straighteners containing these ingredients must be labeled “contains alkali, avoid contact with eyes, can cause blindness, keep out of reach of children.” The professional hair straighters must be labeled “for professional use only, avoid contact with eyes, can cause blindness.” Depilatories containing these ingredients must include the following on the label: “Keep out of reach of children, avoid contact with eyes.” Calcium Hydroxide may be used at a maximum of 7% in hair straighteners that also contain a guanidine salt. It is also permited in depilatories as a pH adjuster if the pH does not exceed 12.7, and in other products if the pH does not exceed 11. Hair straighteners and depilatory products containing this ingredient must be labeled “Contains alkali, avoid contact with eyes, keep out of reach of children”, hair straighteners must also be labeled “can cause blindness” (see Annex III). Magnesium Hydroxide may be used in cosmetics and personal care products marketed in the Europe according to the general provisions of the Cosmetics Regulation of the European Union.

EU Cosmetic Regulation

More Scientific Information:

Sodium Hydroxide, Calcium Hydroxide, Magnesium Hydroxide and Potassium Hydroxide are inorganic bases. Inorganic bases are alkalies which contain no carbon atoms. When placed in water, Sodium, Calcium, Magnesium and Potassium Hydroxide separate into cations (positively charged sodium, calcium, magnesium or potassium) and hydroxide anions (negatively charged). The hydroxide anions serve to decrease the acidity of water (increase pH). In cosmetics and personal care products, Sodium Hydroxide, Calcium Hydroxide, Magnesium Hydroxide and Potassium Hydroxide function as a pH adjusters. Magnesium Hydroxide also functions as an absorbant.

Resources:

Find out more about the regulation of Food Additives by the Food and Drug Administration

Find out more about the regulation of Over-the-Counter drugs by the Food and Drug Administration