Thioglycolic acid

Thioglycolic acid is a colourless, liquid compound (molecular formula C2 H4 O2 S), which chemically belongs to the group of thiols, which contain a sulphur atom instead of an oxygen atom. The acid is miscible with water, ethanol, chloroform, toluene and diethylether. The salts/esters of thioglycolic acid are called thioglycolates.

Derivatives of thioglycolic acid are used in hairdressing to apply a permanent wave. The perming liquid used is usually 1%-10% ammonium thioglycolate, an ammonium salt of thioglycolic acid (called developer in the hairdressing field). This causes a molecular shift within the keratin (the disulfide bridges between 2 cysteine units of the keratin are dissolved).

Ammonium thioglycolate: From an allergological point of view, ammonium thioglycolate has a considerable sensitizing potency. In a screening of eczema patients in the hairdressing profession, contact sensitisation to this thioglycol compound was detected in 12.3% of the subjects.

Glyceryl thioglycolate (INCI) is also used as permanent wave fluid.

Potassium thioglycolate: The potassium salt of thioglycolic acid is used as depilatory agent under the INCI designation "Potassium thioglycolate".

Calcium thioglycolate: The calcium salt of thioglycolic acid is used as depilatory under the INCI designation"Calcium thioglycolate".

When heated, mercaptoacetic acid decomposes to form toxic, unpleasant smelling vapours (hydrogen sulphide and sulphur oxide).

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