Does the pure plant hair dyeing advertised in the market really not cause harm to the body?

Does the pure plant hair dyeing advertised in the market really not cause harm to the body? No matter what kind of dyeing method is used, it is harmful to hair, and easily using products without certification will threaten people's health. I still have the following views on this:

1. What is plant hair dyeing? What are the characteristics of plant hair dyeing?

Plant hair dyeing means that the hair dyeing substance contacts with the stratum corneum, and gradually absorbs on the stratum corneum surface after wetting, and then enters the stratum corneum through the cell membrane and further permeates and diffuses into the medulla of the hair, thus changing the color of the hair. Plant hair dye is a substance that uses pigments extracted from plant stems and leaves to dye hair.

Second, what is the difference between plant component dyeing and chemical component dyeing?

In terms of health and safety, natural plant hair dyes are basically safe to the human body and will not cause primary irritation, except for allergic phenomena to individual people. In terms of environmental protection, because it is a renewable resource from nature, it can be degraded naturally and will not cause additional adverse effects on the environment. Chemical hair dyeing is a kind of hair dye that uses harmful chemical components extracted artificially to color hair to change its own color and beautify it.

Three, hair dyes are divided into several categories according to persistence?

Hair dyes can be divided into three categories according to the length of color retention time: the first category is temporary hair dyes, which generally dye the hair surface with water-soluble dyes. This hair dye has poor color fastness and is easy to rinse. Generally, alkaline, acidic and dispersible polymer dyes can be used to make liquid and paste smears. The dyes are dissolved in aqueous polymer liquids and are often used in temporary occasions such as performances. Second, short-term hair dyes, such as foam hair dyes, are more resistant to cleaning; The third is permanent hair dye, which does not fade after dyeing, but the dyeing effect is longer than the other two.