Demipermanent
Formulated to deposit color on the hair shaft without lightening it. This formula has smaller molecules than those of temporary tinting formulas, and is therefore able to penetrate the hair shaft. It also lasts longer than semi permanent hair keeping color intact up to 15-24 shampoos.
The American Board of Certified Haircolorists and most major manufacturers of hair color now say one should color the new growth area with a permanent color to cover gray and touch up or refresh the ends and length of the hair with a compatible shade of demi permanent color to protect the condition of the hair.
Permanent
This is mixed with developer and remains in the hair shaft until new growth of hair occurs. It's used to match, lighten, and cover gray hair. Permanent hair color generally contains ammonia, oxidative tints, and peroxide. The allergic reaction that comes from hair dye is generally one of sensitization to p-phenylenediamine (PPD). The reaction will most likely occur each time one dyes one's hair and will probably get worse each time. The sensitization from the ingredients in hair color can extend to sensitization of other products of same or similar composition, including but not limited to the dye used in textiles, sunscreen, rubber, and/or certain medications.
Henna is a deposit-only hair color whose active component, lawsone, binds to keratin and is therefore permanent. Henna may be removed with mineral oil; however, it is considered "permanent" because it does not wash out with shampoos or rinses. It is often mixed with other plant dyes, such as indigo, turmeric, and senna, to change the color. Allergy to henna is much rarer than allergy to permanent hair colors. It is also considered a conditioning treatment.
Using a plant-based color, specifically henna, can cause problems later when trying to do a permanent wave (perm) and other permanent hair color. Discoloration can occur on hair that has been previously tinted with henna; hennaed hair typically cannot be curled. Breakage could also be an issue.
