As a result of their composition, cosmetic agents can serve as a growth medium for germs and microorganisms. These germs can result in the microbial contamination of the user and alter the ingredients of the cosmetics so as to create substances having adverse effects such as sensitization or skin irritation. To avoid these undesired consequences while ensuring a certain minimum shelf life of the cosmetics, they must be preserved. Since preservatives themselves can have irritative potential, the use thereof in cosmetics is strictly regulated.
Cosmetic products for changing the hair color generally include direct dyes and/or oxidation dye precursors. During the use of direct dyes, the ready-to-use dyes are applied to the keratin fibers.
The addition of preservatives can be required especially with level 1 colorations. Level 1 colorations include no oxidation dye precursors, but rather only direct dyes. To prevent damaging the hair, there is a trend toward setting level 1 colorations to neutral to slightly acidic pH values. Particularly if no large quantities of alkalizing agents are used, level 1 colorations can be contaminated by germs. This contamination must be prevented through the addition of maximally effective and well suited preservatives.
Oxidation dye precursors are included in oxidative colorants. These are so-called developer components and coupler components, which form the actual colorants only under the influence of oxidizing agents (generally hydrogen peroxide). Oxidizing agents are characterized by long-lasting coloring results.
Oxidative colorants are usually applied in an alkaline medium and require the presence of hydrogen peroxide. Since hydrogen peroxide itself has biocidal and preserving characteristics, it is normally not necessary to also add additional preservatives to oxidative color-changing agents other than hydrogen peroxide. Under certain conditions, however, the preservation of oxidative colorants can be necessary.
Oxidative coloration takes a toll on hair, and it is for that reason that it is generally repeated only after a period of 6 to 8 weeks. Within this time period, however, the hair grows in and the non-dyed hairs become visible at the base. This difference in color between dyed and non-dyed hair is often perceived by the user as highly unattractive. One possibility for concealing these color differences is the root touch-up. In a root touch-up, only the root is dyed—for example 2 to 3 weeks after the regular dyeing of all of the hair. Since this root touch-up is performed as additional coloration between the regular whole-head coloration procedures, it constitutes an additional stress for the hair and should be as gentle as possible. Appropriately, the agents used for root touch-ups are either only direct dyes, or hydrogen peroxide is used in very small concentrations. The reduction of the concentration of the hydrogen peroxide or the complete omission thereof can render the use of additional preservatives necessary.
Moreover, products for root coloration are often packaged such that their quantity is enough for several root touch-ups. The bottle or tube containing the coloring cream is repeatedly opened and closed by the user in order to remove the portion required for the individual root treatment, thereby creating the danger of contamination of the product with germs or microorganisms. The preservation of the colorants becomes necessary for this reason as well.
It is therefore desirable to provide effective preservatives and preservative mixtures that are well suited for hair dyes. The preservatives should prevent the colonization of the colorant and the scalp with undesired germs while not or not substantially harming the natural skin flora.
Moreover, it should be possible to color the keratin fibers in bright, intense colors even when using the preservatives. Particularly, the use of the preservatives should not result in any color shifting, and reactions between colorants and the preservatives as well as the formation of undesired byproducts should also be avoided. Furthermore, the fastness characteristics of the colorations should also not be negatively affected by the use of the preservatives.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with this background of the invention.