In 2007, the Ministry of Health clearly pointed out that henna could not be used as hair dye in its reply. People who dye their hair are about three times more likely to suffer from blood diseases and lymphoma than ordinary people. Animal experiments have proved that henna can induce spontaneous abortion in pregnant women, and it can also cause dizziness, loss of appetite, fatigue, transient amnesia and other symptoms when the dose is large.

The dyeing principle of nail pollen is that nail pollen contains a plant pigment called Sanmohua, which slowly dissociates from the base powder at a high temperature above 60 degrees and a humidity above 100 degrees (especially in an acidic environment, which can accelerate its dissociation speed), and combines with keratin (the main component is amino acid) in hair to generate a new coloring substance.

This hair color substance will obviously deepen the color in the air (this is the reason why the hair will deepen after two or three days of nail pollen dyeing), and it will form reddish brown, brown, brown and other colors according to the difference of hair quality and background color in the sun.

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The reason why henna hair dye is sought after may be influenced by propaganda such as "from India, used by the royal family, extracted from pure natural plants and without stimulation", but pure natural hair dye does not exist. The hair dye extracted from plants can't make the color and hair last forever. Hair dyes that can be colored for a long time must add chemical components, just a matter of how much.

Dyeing hair really gives people a sense of beauty, but we must see its influence on the body. Pregnant women and lactating women are not suitable for contact with chemical dye products, and try to reduce the number of hair dyeing. It is best not to repeat hair dyeing within three months, and skin allergy test should be carried out before hair dyeing.

Baidu encyclopedia-Henan fen