Ingredient review
Ammonium Thiolactate
INCI: Ammonium Thiolactate
A strong chemical that breaks hair bonds for removal or straightening, but can irritate skin and requires careful use.
In plain English
Ammonium thiolactate is a chemical that works by breaking the protein bonds in hair, making it weak enough to be wiped away or straightened. It's found in hair removal creams and some relaxers. Because it's strong, it can cause skin irritation, redness, or burns if left on too long or used on sensitive skin. It's not a moisturizer or treatment—it's a functional ingredient for changing hair structure.
Quick decision guide
Read the cautions before using
Ammonium Thiolactate 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 Thiolactate.
- 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
moderateThere is useful support, but formula details and claim strength still matter.
What it is
Ammonium thiolactate is a synthetic ammonium salt of thiolactic acid. It belongs to a class of chemicals called thiols (or mercaptans) that are known for their strong reducing properties. In cosmetics, it's used specifically to break disulfide bonds in keratin, the protein that gives hair its strength and shape.
How it works
When applied to hair, ammonium thiolactate reduces (breaks) the disulfide bonds that hold the hair's protein structure together. This softens the hair shaft, allowing it to be easily wiped away (in depilatories) or reshaped (in straighteners). The effect is temporary—new hair growth will have its original bonds. The process is alkaline, so products often include a high pH to maximize effectiveness.
Pros
Effective hair removal
Breaks hair bonds quickly, allowing easy wipe-away removal without shaving nicks.
Temporary straightening
Can relax curls or waves for a few weeks, offering an alternative to heat styling.
Cons and cautions
Skin irritation risk
Commonly causes redness, stinging, or burns, especially if left on longer than directed or used on sensitive areas.
Unpleasant odor
Has a strong sulfur-like smell that many find off-putting during and after use.
Best for
- People looking for a depilatory cream for body hair removal
- Those seeking a chemical hair straightener for coarse hair
Use caution if
- Anyone with sensitive, broken, or irritated skin
- People with a history of allergic reactions to depilatory products
Usage tips
Safety summary
Ammonium thiolactate is effective but carries a high irritation risk. It is safe for occasional use when instructions are followed exactly, but it should not be used on broken skin, and a patch test is essential. Prolonged or frequent use can lead to chemical burns or hair damage.
Research notes
Research confirms ammonium thiolactate's role as a reducing agent in depilatories and relaxers. Studies highlight its potential for skin irritation, with safety assessments recommending concentration limits and warning labels. Evidence is moderate, with most data coming from industry safety panels rather than independent clinical trials.
Common label clues
- Typical concentration
- 2% to 10% in depilatory products
- Regulatory status
- Approved for use in cosmetics in the US (FDA) and EU (CosIng) with concentration limits and labeling requirements for depilatory products.
- Common uses
- Depilatory creams, Hair straighteners, Hair relaxers
- Environmental note
- Thiol compounds can have a strong odor and may be irritating to aquatic life if rinsed down drains in large quantities. Use as directed and dispose of product waste properly.
Good to know
- Ammonium thiolactate is often used in combination with calcium hydroxide or other alkalizers to raise pH for better performance.
- Products containing this ingredient are typically not recommended for use on the face or bikini area due to higher sensitivity.
Common questions
What is Ammonium Thiolactate in beauty products?
Ammonium thiolactate is a chemical that works by breaking the protein bonds in hair, making it weak enough to be wiped away or straightened. It's found in hair removal creams and some relaxers. Because it's strong, it can cause skin irritation, redness, or burns if left on too long or used on sensitive skin. It's not a moisturizer or treatment—it's a functional ingredient for changing hair structure.
What does Ammonium Thiolactate do in a beauty product?
When applied to hair, ammonium thiolactate reduces (breaks) the disulfide bonds that hold the hair's protein structure together. This softens the hair shaft, allowing it to be easily wiped away (in depilatories) or reshaped (in straighteners). The effect is temporary—new hair growth will have its original bonds. The process is alkaline, so products often include a high pH to maximize effectiveness.
Is Ammonium Thiolactate safe for most people?
Ammonium thiolactate is effective but carries a high irritation risk. It is safe for occasional use when instructions are followed exactly, but it should not be used on broken skin, and a patch test is essential. Prolonged or frequent use can lead to chemical burns or hair damage.
Who should be careful with Ammonium Thiolactate?
Anyone with sensitive, broken, or irritated skin People with a history of allergic reactions to depilatory products
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.