Posted by L’Oréal submitted a patent application [1] for removing color from hair comprising a sulfur-based reducing agent, such as a sulfite, bisulfite, at least one cyclodextrin ( β-cyclodextrin is highlighted) and at least one solvent, such as water.
Consumers often desire to change the color of their hair. For example, as a person ages, the hair follicle loses its natural pigment, resulting in grey, silver, or white hair. It is common for consumers to color their grey hairs, for example to match their natural hair color. Similarly, consumers may wish to change the color of their hair from that of their natural color. For example, consumers often wish to lighten or darken their hair color.
The process of altering the color of hair is complex, however, particularly when permanent (oxidative) hair dyes are used. In some cases, the process requires that the natural pigment (melanin) in the hair fiber be destroyed before dye molecules of the desired color are added. This process is typically used when one desires to change the color of the hair to a shade lighter than their natural color, by dissolving the melanin with an oxidizing agent before the oxidative dye molecules penetrate the hair fiber where they achieve the target shade by undergoing a chemical reaction with an oxidizing agent. If the user wishes to change the color of the hair to a shade darker than their natural shade it may not be necessary to destroy the melanin in the hair fiber, but the oxidative dye must still undergo a reaction with an oxidizing agent to achieve the target shade.
However, if the user has previously changed the color of the hair with a first oxidative dye wishes to alter the color of their previously-colored hair to achieve a second color or shade, the first oxidative dye, which is not able to be washed out, must be neutralized so that it no longer imparts the first color to the hair fiber. Although there are known methods for removing the first color from the hair by neutralizing (reducing) the first oxidative dye molecules, these methods are not completely satisfactory because the first oxidative dye molecules can re-oxidize, thus interfering with the ability of the consumer to achieve the desired second color or shade. Other known methods for removing the first color from the hair use oxidizing agents, but these compositions are harsh and lead to damage to the hair causing the hair to be weak, brittle, and have an unhealthy appearance.
It has been discovered by the inventors that a synergistic combination of components removes oxidative dyes from hair in a manner that also prevents the dyes from re-oxidizing. The combination of components therefore can be used to alter the overall color of the hair by removing all or substantially all of the previously-applied color, or to remove only certain colors or shades, in order to vary the color or tone of the hair without removing all color (e.g. to alter the color of the hair to a warmer or cooler tone).
The combination of components has the additional benefit that the hair color removing compositions do not have the traditional strong odor associated with typical color-removing compositions, which odor most users find offensive.