Metallic salts are metallic compounds contained in most store-bought hair dyes. Metallic salts change the hair color when they chemically react with sulfur contained in hair protein. Metallic salts have been used in hair dyes since the 1800s.
Hair dye containing metallic salts leaves residue on the hair that increases each time it is applied to hair. As a result, hair will become progressively darker than the desired shade with repeated applications of this type of hair dye. The hair will lighten only after metallic salts are stripped from hair. Metallic salts are difficult to remove from the hair and may require professional color correction, which is much more costly than a trip to the salon for a routine hair color or highlight. Metallic salts will also dry out and harden hair with repeated use.
When deciding on a new hair color, it is best to take a trip to the salon. While it may cost more, stylists are educated on hair color theory such as undertones, levels and shades. A professional stylist is able to formulate the client's desired hair color with professional products that are healthier for the hair than store-bought dyes containing metallic salts. An experienced, well-trained stylist using quality hair products can often achieve better results than results achieved at home with boxed dyes.