2%, but strong enough to cause cancer.
In 1994, the Journal of the American College of Toxicology (now known as the International Journal of Toxicology) published The Addendum to the Final Report on the Safety Assessment of Hydroquinone. Its conclusion stated that “hydroquinone is a potent cytotoxic agent that causes mutations and alterations to DNA, and that it should not be used in any leave-on type of product; it is safe for rinse-off products when used in concentrations less than 1 percent."
Hydroquinone is immunogenic, it's a carcinogen, some people get contact dermatitis from using it, and in rare cases, people have experienced hypopigmentation after overusing hydroquinone because the chemical is photosensitive. This means that your skin will become darker. The condition is called exogenous ochronosis.
answered 1 year, 9 months ago
answered 2 years, 1 month ago
2% I use it and haven't had anything bad happen to my skin and i'm really sensitive
answered 2 years, 3 months ago