Both demi-permanent and semi-permanent hair color dyes can be applied at a salon or at home. The main differences between demi and semi-permanent hair color are the duration the color lasts and how the dye penetrates the hair shaft.
Semi-permanent hair color does not contain any peroxide while demi-permanent hair color may contain low levels of ammonia or peroxide.
Demi-permanent hair color lasts up to 20 shampoos while semi-permanent hair color only lasts up to 12 shampoos.
Semi-permanent hair color deposits dye only on the outermost layer of hair. Demi-permanent hair color deposits dye between the cuticle and cortex of the hair shaft, making it last longer.
According to Salon East NYC, semi-permanent is a good solution for hair that has 20 percent or less gray in it. People with a higher percentage of gray hair will see better results with a demi-permanent hair color.
Both semi-permanent hair dye and demi-permanent hair dye enhance natural color tones. Unlike semi-permanent hair dye, demi-permanent hair dye has the ability to lighten hair color.