Approximately 100 years ago, humans invented artificial hair dye. Today, hair coloring has become a common practice for many. Young people use it to showcase fashion, while middle-aged and elderly individuals use it to appear younger. However, media reports about the potential hazards of hair dye, such as cancer and kidney damage, have never ceased. Which hair dye habits can lead to increased harm? And what methods can reduce the damage caused by dyeing hair?

Potential Hazards of Hair Dye

“According to epidemiological statistics, 50% of people will dye their hair at least twice in their lifetime,” said Dr. Liang Yanhua, Associate Professor of Dermatology at the Southern Medical University Southern Hospital and Assistant Researcher at Yale University School of Medicine. The safety of hair dyeing is indeed crucial. Frequent dyeing can pose four major risks to the human body:

The most frightening harm: potential carcinogenicity. Researchers at Yale University investigated women who started dyeing their hair before 1980 and found that over one-third of them developed lymphoma. Another survey conducted by the American Cancer Society on 13,000 women who dyed their hair indicated that they had a 3.8 times higher risk of leukemia compared to non-dyed women. However, a 40-year study by Spanish scientists found that the probability of hair dye carcinogenesis was only slightly increased. Dr. Yang Shuxia, Deputy Chief Physician of Dermatology at Peking University First Hospital, told reporters that there is considerable research internationally on whether hair dyeing causes cancer, but there is still controversy over whether it does. Nevertheless, since the late 1970s, some components of hair dye that have been proven to cause tumors are gradually disappearing from their formulas.

The most common harm: skin allergies. Dr. Yang Shuxia explained that p-phenylenediamine is a major component of hair dye, which can make the hair color more durable but is also a strong allergen, causing skin allergies in sensitive individuals, with contact dermatitis being the most common. Dr. Yang Shuxia stated that as long as the hair dye meets national standards and is used in the required amount, it is still safe.

The most insidious harm: damage to the liver and kidneys. Dr. Yang Shuxia said that in recent years, although the quality and safety of hair dye products have improved, some products on the market add heavy metals such as lead, mercury, and arsenic to enhance dyeing effects. The lead content in some products is even 5-10 times that of lead in paint, which can cause chronic damage to the body with long-term use, leading not only to symptoms of lead poisoning such as dizziness, numbness of limbs, and abdominal pain but also damaging the function of organs such as the liver and kidneys.

The most embarrassing harm: exacerbating hair loss. Dr. Liang Yanhua said that many patients experience hair loss due to frequent dyeing. This is because certain aromatic compounds such as p-phenylenediamine in some hair dyes can penetrate into the vital part of the hair – the cuticle, undergo oxidation reactions, and subsequently cause dryness, breakage, and even hair loss.

Common Hair Dyeing Mistakes

Dr. Yang Shuxia said that the harm of hair dyeing to the human body is also closely related to our hair dyeing habits. Factors such as weather and color, which seem unrelated, can exacerbate its harm.

Hair dyeing on smoggy days may increase cancer risk. According to the international authoritative scientific journal “Materials,” hair dyes contain harmful substances such as secondary amines, which as fixing agents for dyes can make colors more stable but can penetrate into the hair and skin and remain for weeks, months, or even years. They can react with tobacco smoke or exhaust gases in the air to form strong carcinogenic chemicals such as nitrosamines. Therefore, dyeing hair on smoggy days may pose a higher risk of cancer.

Darker and brighter colors may pose a higher cancer risk. Dr. Liang Yanhua mentioned a recent study in the United States that suggests that the darker the hair dye color, the higher the risk of carcinogenesis. Dr. Yang Shuxia also mentioned that in general, darker or brighter hair dyes have higher contents of p-phenylenediamine. Hair dyes containing p-phenylenediamine are mostly permanent, favored by people for their longer-lasting effects, but they cause greater harm to the hair and scalp. After dyeing with semi-permanent or temporary hair dyes, the color fades after 5-10 washes, but the damage is less.

Dyeing and perming together can cause significant damage. Many people choose to dye and perm their hair at the same time for convenience. However, the hair solutions used in perming often contain alkaline ingredients and oxidants, which can damage the outer layer of the hair, making the internal structure of the hair unprotected, leading to yellowing, brittleness, lack of elasticity, and luster. At this time, dyeing the already damaged hair is undoubtedly adding insult to injury.

Dyeing despite unsuitability. Dr. Yang Shuxia said that the following five groups of people are better off not dyeing their hair, otherwise, the damage will be greater: ① Those allergic to hair dye, any ingredient in hair dye may trigger allergies; ② People with damaged scalp or skin diseases, the toxic and harmful substances in hair dye are more easily absorbed into the body; ③ Elderly people with weak bodies and impaired liver and kidney functions, their detoxification ability weakened, and the risk of poisoning increased; ④ Pregnant and lactating women, whose bodies are more sensitive during pregnancy, making them more prone to allergies from hair dye; ⑤ People with a family history of cancer, who are more prone to tumors than the general population and should dye their hair as little as possible.

9 Tips for Safely Dyeing Hair

The desire for beauty is universal. How can we balance beauty and health? Experts offer the following advice:

Don’t wash your hair the day before dyeing. The oil secretions on the scalp can protect it well, to some extent, preventing harmful substances from penetrating the scalp. Therefore, it is best not to wash your hair the day before dyeing, and don’t use conditioner, as it will affect the coloring effect. Also, avoid oil treatments for a week before dyeing.

Do a skin test before dyeing. Before dyeing, apply a small amount of hair dye to the delicate skin behind the ear or on the inner arm and observe for 2-4 days. If there are no redness, bumps, blisters, etc., then proceed with dyeing.

Apply lotion around the hairline. Before applying the hair dye, apply lotion or petroleum jelly around the hairline. This way, if the dye gets on the skin, it can be washed off easily. Before dyeing, you can also remind the hairdresser to apply the dye about 1 cm away from the roots to avoid direct contact with the scalp.

Do not mix hair dyes from different brands. Do not mix hair dyes from different brands to avoid unnecessary chemical reactions and the generation of toxic substances.

Dye no more than twice a year. Avoid dyeing hair frequently, and let at least 3 months pass between dyeing sessions. Middle-aged