Ammonium Thioglycolate

What it is

Ammonium thioglycolate is the ammonium salt of thioglycolic acid and the classic active for reshaping hair — in perms as well as in thio-based straightening systems. It acts as a reducing agent: it breaks part of the disulphide bonds that give keratin its shape. While those bonds are open the hair can be moved into a new form; the subsequent fixing step with an oxidising agent closes them again in the new arrangement.

The substance is therefore not a conditioning ingredient but a process active: it works during the treatment and is rinsed out afterwards. The reaction takes place in the alkaline range because that is where the reducing agent is effective. Effect and burden thus come from the same source and cannot be controlled independently of one another.

Why

• The substance works because it alters the fibre. There is no permanent reshaping without an intervention in the structure. “Gentle reshaping” describes the control of concentration, pH and processing time — not the absence of change.
• Time is a safety parameter here. If the intended processing time is exceeded, more bonds are broken than intended and the result is over-processed hair. The manufacturer's instructions on processing time, intermediate checks and fixing are therefore the most important part of the application, not a formality.
• Why the classification reads “increased attention”: because of the irritant potential for skin and eyes and because of the known role of thioglycolates in occupational skin problems in hairdressing. That is a statement about repeated, unprotected contact during handling — and expressly not a finding that a properly performed treatment harms the client.
• Occupational and client exposure are two different questions. The client has a few short applications a year, after which the product is rinsed out. The professional potentially works with it every day, hands in the product. The question of gloves therefore belongs in the assessment.
• Odour is not a measure of hazard. Thioglycolates smell distinctly of sulphur; that indicates volatile constituents, not the level of risk. The reverse holds just as much: a low-odour reshaping product is not automatically milder, it may simply work with a different reducing agent.

When the assessment differs

• Pre-damaged, previously chemically treated or bleached hair: the risk of over-processing is markedly higher here. A strand test and the manufacturer's instructions govern.
• Broken, irritated or inflamed scalp skin: not a suitable starting point for an alkaline reshaping treatment. The manufacturer's instructions take precedence.
• Occupational skin contact without gloves: the most important differing case. Repeated contact with reducing agents combined with wet work is the constellation from which occupational hand eczema develops.
• Eye contact: irritating, practically relevant during application and rinsing.
• Several chemical treatments at the same appointment: not assessed here. The manufacturer's specifications and the assessment of the hair itself govern.

Open questions

• Concentration and pH of the actual product: not available. Both largely determine how strongly the product acts; without them no robust product statement is possible.
• Regulatory status: rules exist for thioglycolates on maximum levels, on the distinction between professional and general use, and on warning statements. They have not been checked here and are deliberately not quoted second-hand.
• Data on occupational skin disease in hairdressing: not evaluated here. The classification follows the substance group and the situation of use, not an evaluation of studies.
• Delimitation from other reshaping systems, for instance cysteine- or sulphite-based ones: not the subject of this assessment. Transferring these statements to those systems is not permissible.

Related substances

Applies to: Reducing agents for reshaping

• Cysteamine HCl — Reshapes the hair and adds bounce

Further substances from the same group for which a long-form assessment already exists.