Cosmetics

The #1 reason irritation testing gets rejected? You’re using the wrong exposure route. We’ve reviewed dozens of irritation studies that looked solid—until they reached regulators. The […]

Hair dyes use chemicals to change the color of the hair. There are three main types of hair dye: permanent, semi-permanent, and temporary. Permanent hair dyes, which make up about 80% of currently marketed hair dye products, use colorless dye intermediates and dye couplers. In the presence of hydrogen peroxide, the intermediates and couplers react with one another to form pigment molecules. Darker colors are formed by using higher concentrations of intermediates.