The hair dye is still within the warranty period, and there is no other change, so it can be used. However, hair dyes that have been used for more than half a year cannot be used. Hair dyeing interval is more than 3 months. Don't use different brands of products at the same time, because chemical reactions may occur between them, producing toxic substances and increasing the probability of allergies.
Don't dye your hair too often, at most three times a year. Only new hair can be dyed. One to two weeks before dyeing, strengthening hair care can reduce the damage to hair and make it easier to dye.
One week before dyeing, don't use shampoo, hair scale conditioner, or conditioner and conditioner. These products will form a protective film on the hair to prevent dyes from entering. Shampoo with deep cleaning effect should be used.
Try not to wash your hair two days before dyeing, let your hair secrete oil and form a natural protective film to protect hair follicles. Do a local allergy test 48 hours before dyeing your hair.
Extended data:
Experts suggest that you should not dye your hair more than twice a year. Patients with hypertension, heart disease and asthma should not dye their hair. In addition, couples who are ready to give birth, pregnant women and lactating women are not suitable for dyeing their hair.
Long-term use of hair dye is harmful to health. American experts examined 160 popular hair dyes, and found that 150 of them had carcinogenic effects. For example, in oxidized hair dyes, there is a substance called 2-4 amino anisole, which is most likely to accumulate in the human body and promote cell proliferation. In general, if the hair dye is used for 10 years, human skin can cause cancer as long as it absorbs 1% of this substance.
In addition, the use of hair dye will make the immune function of human body disorder, which will lead to lupus erythematosus. Other hair dyes can cause allergic dermatitis and allergic conjunctivitis. Therefore, scientists warn people that hair dyes should be used with caution.
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