Chapter 4 139 that have been used in combination with ammonia and hydrogen peroxide at pH 10 to produce vibrant shades either alone or in combination with oxidative dyes.21 The cationic charge increases hair interactions and as a consequence wash fade is reduced.22 O N N O NH2 N N N N NH2 Cl- N N N N N Cl- Basic Red 51 Basic Blue 124 Basic Orange 31 The two dyes whose structures are outlined below have been used in combination with persulfate bleach in an attempt to simultaneously deliver significant lightening and color to the hair.23 O2N N N N OH OH - O 3 S N N HO Acid Orange 7 Disperse Red 17 Semi-permanent Products These products are designed to deliver color with no lightening where the color lasts for 5-10 washes.24 Generally the consumers who choose these products want a quick and easy treatment either to add a small amount of color or to cover a low level of gray. In addition to dyes, the product will include an alkalizer such as aminomethyl propanol to aid dye diffusion by swelling the hair during the application process. The dyes are trapped inside when the pH drops during the washing process, giving the dyes some washing resistance. One issue with these dyes can be uneven application on damaged hair where the tips of the hair are more porous than the roots leading to color “grabbing” at the tips.25 The best option used to avoid this issue is to include several dyes in the formulation with similar colors but different absorption rates to try and even the color from root to tip. The products can also stain skin.