Ingredient review
Ammonium Bisulfite
INCI: AMMONIUM BISULFITE
Ammonium bisulfite is a chemical reducing agent used in professional hair treatments, but it can be irritating and is not common in everyday skincare.
In plain English
Ammonium bisulfite is a chemical that breaks down the protein bonds in hair, allowing it to be reshaped into curls or straightened. It works by reducing disulfide bonds, which are like tiny bridges that give hair its shape. This ingredient is mainly found in salon perm or relaxer kits, not in daily-use shampoos or conditioners. Because it can be irritating to the skin and scalp, it's typically used by professionals and rinsed out quickly.
Quick decision guide
Read the cautions before using
Ammonium Bisulfite can be useful, but watch for some 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 Bisulfite.
- 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
moderateCan bother some users, especially with frequent use, damaged skin, or strong companion ingredients.
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 bisulfite is an inorganic salt that acts as a reducing agent. In cosmetics, it is used to break and reform disulfide bonds in hair keratin, enabling permanent waving or straightening.
How it works
It chemically reduces (breaks) the disulfide bonds in hair keratin, making the hair temporarily flexible. After the hair is reshaped (curled or straightened), an oxidizing agent (like hydrogen peroxide) is applied to reform the bonds in the new shape.
Pros
Effective reshaping
Ammonium bisulfite reliably breaks hair bonds for lasting curls or straightening, often with less odor than thioglycolate-based formulas.
Lower pH option
It works at a slightly acidic pH, which may be less damaging to the hair cuticle compared to alkaline relaxers.
Cons and cautions
Irritation risk
It can cause redness, stinging, or irritation on the scalp and skin, especially if left on too long or used on broken skin.
Not for daily use
This is a strong chemical treatment ingredient, not found in everyday shampoos or conditioners, and misuse can lead to hair breakage.
Best for
- Individuals seeking professional perm or straightening treatments
- People with resilient hair that holds shape well
Use caution if
- Those with sensitive scalp or skin conditions like eczema
- Pregnant or nursing individuals (due to lack of safety data)
Usage tips
Safety summary
Ammonium bisulfite is considered safe for professional use in hair waving and straightening when used as directed. However, it can cause skin and eye irritation, and repeated exposure may lead to sensitization. It is not recommended for leave-on or daily-use products.
Research notes
Research supports its efficacy as a reducing agent for hair reshaping. Safety assessments by the Cosmetic Ingredient Review (CIR) and EU SCCS note irritation potential but deem it safe at low concentrations in rinse-off products. Limited long-term human data exists for chronic exposure.
Common label clues
- Typical concentration
- Typically used at 1–5% in professional hair products
- Regulatory status
- Approved for use in cosmetics in the EU and US, but concentration limits and labeling requirements apply. In the EU, it is listed in Annex III (restricted substances) for hair products.
- Common uses
- Hair perms, Hair relaxers, Hair straightening treatments
- Environmental note
- Ammonium bisulfite can contribute to sulfur emissions during manufacturing; proper waste treatment is needed to avoid environmental harm.
Good to know
- Ammonium bisulfite is often used in 'acid perms' which are gentler than alkaline perms but still require professional application.
- The ingredient has a strong sulfur-like smell during use, which dissipates after rinsing.
Common questions
What is Ammonium Bisulfite in beauty products?
Ammonium bisulfite is a chemical that breaks down the protein bonds in hair, allowing it to be reshaped into curls or straightened. It works by reducing disulfide bonds, which are like tiny bridges that give hair its shape. This ingredient is mainly found in salon perm or relaxer kits, not in daily-use shampoos or conditioners. Because it can be irritating to the skin and scalp, it's typically used by professionals and rinsed out quickly.
What does Ammonium Bisulfite do in a beauty product?
It chemically reduces (breaks) the disulfide bonds in hair keratin, making the hair temporarily flexible. After the hair is reshaped (curled or straightened), an oxidizing agent (like hydrogen peroxide) is applied to reform the bonds in the new shape.
Is Ammonium Bisulfite safe for most people?
Ammonium bisulfite is considered safe for professional use in hair waving and straightening when used as directed. However, it can cause skin and eye irritation, and repeated exposure may lead to sensitization. It is not recommended for leave-on or daily-use products.
Who should be careful with Ammonium Bisulfite?
Those with sensitive scalp or skin conditions like eczema Pregnant or nursing individuals (due to lack of safety data)
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.