Ingredient review
Ammonium Thioglycolate
INCI: AMMONIUM THIOGLYCOLATE
Ammonium thioglycolate is a potent chemical that permanently reshapes hair, but it requires careful handling due to its strong odor and potential for skin and eye irritation.
In plain English
Ammonium thioglycolate is a chemical that breaks the bonds inside your hair, allowing it to be reshaped into curls or straightened. It's the key ingredient in many perms and relaxers. Because it's strong, it can irritate your skin and eyes, and it has a distinct sulfur smell (like rotten eggs). It's not something you'd find in a daily shampoo or conditioner.
Quick decision guide
Useful, but context matters
Ammonium Thioglycolate can be useful, but watch for high irritation potential.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Ammonium Thioglycolate.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
highMore likely to cause dryness, stinging, peeling, or reactivity if used too aggressively.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
strongThere is a stronger practical or research basis for the ingredient role described here.
What it is
Ammonium thioglycolate is the ammonium salt of thioglycolic acid, a synthetic reducing agent. It is a colorless liquid with a strong, unpleasant odor, commonly used in professional and at-home hair waving and straightening products.
How it works
It works by breaking the disulfide bonds in the hair's keratin protein structure. Once these bonds are broken, the hair becomes soft and pliable and can be set into a new shape (curls or straight). A neutralizer (often hydrogen peroxide) is then applied to reform the bonds, locking in the new shape.
Pros
Effective reshaping
Provides permanent changes to hair texture, allowing for long-lasting curls or straightening that won't wash out.
Widely used
A well-established ingredient in professional and consumer perm and relaxer products, with predictable results.
Cons and cautions
Strong odor
Has a distinct sulfur smell that can be unpleasant during application and may linger on hair for a short time.
Irritation potential
Can cause skin and eye irritation, especially if left on too long or used on broken skin. Always requires careful application and rinsing.
Best for
- People seeking long-lasting curls or straightening
- Those willing to follow safety precautions
Use caution if
- People with sensitive skin, scalp conditions, or allergies to thiols
- Pregnant or nursing individuals (due to strong fumes)
Usage tips
Safety summary
Ammonium thioglycolate is safe for use in hair waving and straightening products when used as directed. However, it is a known irritant and sensitizer, so it should be handled with care. Avoid contact with eyes and broken skin, and use in a well-ventilated area.
Research notes
Extensive research supports its efficacy in permanently reshaping hair. Safety data from the Cosmetic Ingredient Review (CIR) panel and regulatory bodies confirm its safety at typical use concentrations, with warnings about irritation and sensitization.
Common label clues
- Typical concentration
- 5% to 15% in professional products; lower in consumer formulas
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other countries, with concentration limits and labeling requirements for professional use.
- Common uses
- Permanent hair waving, Hair straightening, Depilatory creams
- Environmental note
- Synthetic ingredient; its production and disposal should follow local chemical waste guidelines.
Good to know
- Ammonium thioglycolate is often used in 'acid perms' (pH around 7-8) which are gentler than alkaline perms.
- The odor can be reduced with post-treatment rinses or fragranced conditioners.
Common questions
What is Ammonium Thioglycolate in beauty products?
Ammonium thioglycolate is a chemical that breaks the bonds inside your hair, allowing it to be reshaped into curls or straightened. It's the key ingredient in many perms and relaxers. Because it's strong, it can irritate your skin and eyes, and it has a distinct sulfur smell (like rotten eggs). It's not something you'd find in a daily shampoo or conditioner.
What does Ammonium Thioglycolate do in a beauty product?
It works by breaking the disulfide bonds in the hair's keratin protein structure. Once these bonds are broken, the hair becomes soft and pliable and can be set into a new shape (curls or straight). A neutralizer (often hydrogen peroxide) is then applied to reform the bonds, locking in the new shape.
Is Ammonium Thioglycolate safe for most people?
Ammonium thioglycolate is safe for use in hair waving and straightening products when used as directed. However, it is a known irritant and sensitizer, so it should be handled with care. Avoid contact with eyes and broken skin, and use in a well-ventilated area.
Who should be careful with Ammonium Thioglycolate?
People with sensitive skin, scalp conditions, or allergies to thiols Pregnant or nursing individuals (due to strong fumes)
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.