Potassium Thioglycolate

What Is It?

Thioglycolic Acid is an organic compound that contains a thiol group (-SH) and carboxylic acid. It is a colorless liquid. Thioglycolic Acid and some salts and esters of Thioglycolic Acid, such as Ammonium Thioglycolate, Butyl Thioglycolate, Calcium Thioglycolate, Ethanolamine Thioglycolate, Glyceryl Thioglycolate, Isooctyl Thioglycolate, Isopropyl Thioglycolate, Magnesium Thioglycolate, Methyl Thioglycolate, Potassium Thioglycolate and Sodium Thioglycolate are used in hair coloring products, permanent wave products, hair straightening products and depilatory products.

Why Is It Used?

Thioglycolic Acid and it salts and esters modify hair fibers to facilitate changes to the structure of the fibers, such as with permanent waves or with hair straightening. They are also used to chemically break down hair fibers so that unwanted hair can be removed by simply wiping it from the skin.

Scientific Facts

Thioglycolic Acid and its salts and esters break disufide bonds in the cortex of the hair. After washing, the hair is treated with a mild solution of hydrogen peroxide, which causes new bonds to form, giving hair the rigid structure necessary for permanent waves.

Safety Information

As part of its re-review process Cosmetic Ingredient Review (CIR) re-opened the report on Ammonium Thioglycolate, Glyceryl Thioglycolate and Thioglycolic Acid. Because of similarities in stucture and use in personal care products, the CIR Expert Panel added additional thioglycolate sats and esters to this report. The new report was finalized in 2007 with the following conclusion. Based on the available data, Ammonium Thioglycolate, Butyl Thioglycolate, Calcium Thioglycolate, Ethanolamine Thioglycolate, Ethyl Thioglycolate, Glyceryl Thioglycolate, Isooctyl Thioglycolate, Isopropyl Thioglycolate, Magnesium Thioglycolate, Methyl Thioglycolate, Potassium Thioglycolate, Sodium Thioglycolate and Thioglycolic Acid are safe for use in hair straighteners, permanent waves, hair styling products, and hair dyes and colors at concentrations up to 15.2% (as Thioglycolic Acid). Hair dressers should avoid skin contact and minimize consumer skin exposure. Calcium Thioglycolate, Potassium Thioglycolate, Sodium Thioglycolate and Thioglycolic acid in depilatories are safe when formulated to be non-irritating under conditions of recommended use.

CIR Safety Review: The CIR Expert Panel reviewed the safety of Thioglycolic Acid Ammonium Thioglycolate, Butyl Thioglycolate, Calcium Thioglycolate, Ethanolamine Thioglycolate, Glyceryl Thioglycolate, Isooctyl Thioglycolate, Isopropyl Thioglycolate, Magnesium Thioglycolate, Methyl Thioglycolate, Potassium Thioglycolate and Sodium Thioglycolate. These ingredients are used predominantly in permanent waving lotions at concentrations up to 15.2% (as Thioglycolic Acid). At use concentrations, Thioglycolic Acid and it salts and esters were only slightly toxic in acute single oral and dermal exposures. In repeated dermal tests for extended periods of exposure, these ingredients were toxic. Commercial permanent wave products produced transient conjunctival redness to both rinsed and unrinsed eyes. The results of skin testing for irritation and sensitization of these Thioglycolates depend on the type of test system used. Under occlusive patch testing, the data indicate that these ingredients are cumulative irritants and possibly weak sensitizers, but not under semi-occlusive test conditions.

In clinical patients, mainly hairdressers, Glyceryl Thioglycolate elicited allergic reactions at concentrations down to 0.25%. The CIR Expert Panel noted that all method of hair removal, including waxing, shaving and depilatory products may produce trasient dermal irritation. In their experience, when used according to package directions, depilatory products containing Thioglycolic Acid and/or its salts are practically non-irritating. The CIR Expert Panel concluded that Ammonium Thioglycolate, Butyl Thioglycolate, Calcium Thioglycolate, Ethanolamine Thioglycolate, Ethyl Thioglycolate, Glyceryl Thioglycolate, Isooctyl Thioglycolate, Isopropyl Thioglycolate, Magnesium Thioglycolate, Methyl Thioglycolate, Potassium Thioglycolate, Sodium Thioglycolate and Thioglycolic Acid are safe for use in hair straighteners, permanent waves, hair styling products, and hair dyes and colors at concentrations up to 15.2% (as Thioglycolic Acid). Hair dressers should avoid skin contact and minimize consumer skin exposure. Calcium Thioglycolate, Potassium Thioglycolate, Sodium Thioglycolate and Thioglycolic acid in depilatories are safe when formulated to be non-irritating under conditions of recommended use. Health Canada permits the use of Thioglycolic Acid and its salts in hair waving and straightening products at concentrations equal to or less than 8% with a pH of 7 to 9.5, in hair waving and straightening products for professional use at concentrations equal to or less than 11% with a pH of 7 to 9.5 and and in depilatory products at concentrations equal to or less than 5% with a pH of 7 to 12.7.

Directions for use and product labels must be included.

Thioglycolic Acid and its salts and esters are listed in the Cosmetics Regulation of the European Union and may be used in hair waving or straightening products at 8% for general use and 11% for professional use when the pH is between 7 and 9.5. Thioglycolic Acid and its salts can also be used in depilatories and other hair products which are removed after application at 5% (pH 7 to 12.7) and 2% (pH 7 to 9.5), respectively. Other limitations apply and Conditions of Use and Warnings must be printed on the product label.

EU Cosmetic Regulation

More Scientific Information

Thioglycolic Acid is an organic acid. Ammonium Thioglycolate, Calcium Thioglycolate, Ethanolamine Thioglycolate, Magnesium Thioglycolate, Potassium Thioglycolate and Sodium Thioglycolate are salts of Thioglycolic Acid, while Butyl Thioglycolate, Ethyl Thioglycolate, Glyceryl Thioglycolate, Isooctyl Thioglycolate, Isopropyl Thioglycolate and Methyl Thioglycolate are esters of Thioglycolic Acid. Thioglycolic Acid and its salts and esters are used in hair waving and straightening products, while Thioglycolic Acid and its salts are used in depilatory products.