Beauty ingredient research
Browse the review database to understand what an ingredient is, what it does in a beauty formula, when it is useful, and when it deserves caution across skincare, haircare, bodycare, makeup, and more.
20769
Reviewed ingredients
524
Low-concern standouts
2884
Need usage caution
Ammonium sulfite is an effective reducing agent for hair restructuring but can be irritating and has a strong odor, making it more common in salon treatments than daily-use products.
Irritation
moderate
Source
synthetic
An effective but strong reducing agent for permanent hair restructuring; requires careful handling to avoid scalp irritation and hair damage.
Irritation
moderate
Source
synthetic
A potent reducing agent for hair restructuring, but requires careful formulation and professional handling to minimize scalp irritation.
Irritation
moderate
Source
synthetic
A strong chemical used to break and reform hair bonds for perms or straightening; not for everyday use and requires professional handling.
Irritation
high
Source
synthetic
A strong chemical used to break hair bonds for perms or straightening; effective but can be irritating and requires careful handling.
Irritation
high
Source
synthetic
A strong reducing agent for permanent hair restructuring, but can be irritating and requires careful formulation and use.
Irritation
moderate
Source
synthetic