Many individuals, while anticipating the beauty of a new hair color, often harbor concerns about the potential carcinogenic risks of hair dyes as they inhale the pungent odor during the dyeing process.
01 Are Hair Dyes Actually Carcinogenic?
This question has been the subject of research since the 1960s:
- In 1963, studies found that hairdressers were prone to bladder cancer.
- In 1971, British scholars proposed that hair dyes could increase the likelihood of breast cancer in women.
- In 1977, American researchers confirmed that hairdressers had a higher chance of developing lung cancer.
- In 1978, experts reported that women who frequently dyed their hair had more chromosomal breaks in their lymphocytes.
Subsequently, retrospective studies have suggested that the use of permanent hair dyes may increase the risk of various diseases, including bladder cancer, Hodgkin’s disease, non-Hodgkin’s lymphoma, leukemia, breast cancer, multiple myeloma, ovarian cancer, brain cancer, astrocytoma, and brain tumors.
However, do hair dyes, especially permanent ones, truly cause cancer?
The reality is not so straightforward. The aforementioned studies merely indicate that hair dyes may increase the risk of certain cancers, and these studies did not exclude other carcinogenic factors. Therefore, these studies cannot conclusively establish a positive correlation between hair dyes and cancer incidence.
In 2005, the Journal of the American Medical Association (JAMA) published an article stating that Professor Bahi Takkouche and his colleagues from the University of Santiago de Compostela in Spain conducted a meta-analysis of published research and found that hair dyes do not increase the risk of bladder or breast cancer.
In 2020, one of the world’s top medical journals, the British Medical Journal (BMJ), published an article.
This article, based on a 36-year follow-up study of 120,000 researchers, showed no significant correlation between personal use of permanent hair dyes and the risk of most cancer incidences and cancer-related deaths. The study mentioned that even among participants who had dyed their hair more than 200 times over 36 years, no evidence was found of hair dyes directly inducing cancer.
As research has deepened, some recent studies have shown that the correlation between hair dyes and cancer cannot be substantiated.
02 Why Are There Concerns About Hair Dyes Causing Cancer?
This is primarily due to the presence of a substance called “p-Phenylenediamine” in hair dyes.
p-Phenylenediamine, also known as Ursol D, is an organic compound with the chemical formula C6H8N2. It is one of the simplest aromatic diamines and is widely used as an intermediate.
p-Phenylenediamine reacts with oxygen to produce new colors. It turns black when reacting with 3% hydrogen peroxide and brown with 5% ferric chloride. Additionally, p-Phenylenediamine has a strong affinity for keratin in hair, allowing for better color fixation during the oxidation process, resulting in more durable dyeing effects.
With the addition of p-Phenylenediamine, hair dyes achieved a milestone in color durability. However, its presence also raised health concerns—p-Phenylenediamine is listed as a Group 3 carcinogen by the International Agency for Research on Cancer (IARC) of the World Health Organization in its 2017 edition.
However, its harm is not as significant as we might imagine.
According to the IARC’s definition, Group 3 carcinogens are “substances that cannot be classified based on existing evidence, where evidence of carcinogenicity is inadequate in both animal and human studies, or where animal evidence is sufficient but human studies clearly show no carcinogenic effects, belonging to substances that have been studied and found to have essentially no carcinogenic hazard.”
Therefore, the carcinogenicity of p-Phenylenediamine should not be overly concerning.
China has strict requirements for the dosage of p-Phenylenediamine in hair dyes: the maximum allowable concentration must not exceed 6%. Thus, for hair dyes produced by reputable manufacturers that meet standards, we have no reason to worry about their carcinogenicity.
03 What Are the Differences Between Hair Dyes Costing Tens Versus Hundreds of dollar?
There are various styles of hair dyes on the market, with prices ranging from tens to hundreds of dollar. However, are higher-priced hair dyes necessarily better?
In fact, they are not. Hair dyes on the market can generally be divided into four categories: plant-based hair dyes, metallic salt hair dyes, direct hair dyes, and permanent hair dyes.
1. Plant-based Hair Dyes
Plant-based hair dyes are new types of hair dyes currently under research and development, mainly composed of natural plants or their extracts. However, they actually attach coloring molecules directly to the hair surface, making it difficult to achieve long-lasting effects.
2. Metallic Salt Hair Dyes
The main ingredient is lead acetate. The advantage is good coloration and long-lasting color retention. The disadvantage is that lead, as a harmful substance that can enter the human body, has been listed as a banned substance in many countries.
3. Direct Hair Dyes
Direct hair dyes can be divided into two types: temporary hair dyes and semi-permanent hair dyes.
Temporary hair dyes use large dye molecules that do not penetrate the hair fibers, usually only temporarily adhering to the hair surface to achieve a coloring effect.
Unlike permanent hair dyes, semi-permanent hair dyes use dyes that can enter the hair quality through the outer layer of the hair without oxidation to dye directly.
The advantage of direct hair dyes is that they are safe and cause little damage to the hair; the disadvantage is that the color retention time is short.
4. Permanent (or Oxidative) Hair Dyes
Permanent hair dyes are generally chemically synthesized, consisting of intermediates, couplers, and oxidants. The main components include p-Phenylenediamine and hydrogen peroxide.
Permanent hair dyes mainly utilize the oxidative polymerization reaction of p-Phenylenediamine to produce macromolecular pigments, thereby achieving coloring and color fixation effects.
The hair dyes we have been discussing above are permanent hair dyes. Permanent hair dyes are the most widely used hair dyes, accounting for about 80% of the market share.
When choosing hair dyes, it is important to carefully examine the product’s ingredient list. Many products on the market that claim to be plant-based hair dyes often simply add plant extracts to the hair dye, without changing their essential nature of containing p-Phenylenediamine or even certain heavy metal components.
04 How to Dye Hair Safely?
Although there is no confirmed positive correlation between hair dyes and cancer incidence, some other harmful effects of hair dyes on the human body should not be ignored. To dye hair safely, pay attention to the following points:
1. Do Not Dye and Perm Hair Simultaneously
Hair dyes, especially permanent ones, damage the hair quality during the coloring process, making the hair dry and frizzy. The chemicals used in perming often contain oxidants and alkaline substances, which also greatly damage the hair quality. Simultaneous perming and dyeing will exponentially increase the damage to the hair quality. If time allows, it is recommended to separate perming and dyeing, giving the hair time to recover.
2. Conduct Allergy Tests Before Dyeing
The chemical components in hair dyes, such as hydrogen peroxide, chemical dyes, coupling colorants, as well as some plant components added to certain hair dyes, are allergens that can easily cause allergic reactions during the dyeing process, potentially leading to scalp allergies. Therefore, it is essential to conduct allergy tests before dyeing. You can dilute the hair dye with water and apply it to the inner side of the elbow or behind the ear 48-72 hours before dyeing to observe for any allergic reactions.
3. It Is Recommended Not to Wash Hair Before Dyeing
The oil secreted by the scalp not only protects the scalp from damage by hair dyes but also allows for more saturated hair coloration.
4. Choose Qualified Hair Dyes
China’s “Cosmetics Hygiene Supervision Regulations” explicitly stipulate that hair dye products are one of the nine categories of special-purpose cosmetics and must obtain a special-purpose cosmetics approval number before production and sale. When choosing hair dyes, it is best to select products from reputable manufacturers and pay attention to whether there is a “Guo Zhuang Te Zi” mark on the product packaging. Do not be misled by hair dyes with exaggerated plant-based claims.
Especially before dyeing hair at a salon, remember to verify the packaging of the hair dye with the hairdresser to confirm whether it is a legitimate product.
5. Use Hair Dye Products Correctly According to Instructions
When using hair dye products, it is recommended to carefully read the instructions. Wear disposable gloves during use to avoid direct contact with the hair dye. It is not recommended to use hair dyes when there are skin injuries on the head, neck, or hands. It is best to wait until the skin barrier is fully repaired before dyeing hair.
6. Do Not Dye Hair Too Frequently
It is recommended to have an interval of at least 4 months between each hair dyeing session.
05 Hair Care After Dyeing
To maintain the health of your hair and the vibrancy of your new color, proper hair care after dyeing is essential:
- Wait at least 48 hours after dyeing before washing your hair to allow the color to set.
- Use color-safe shampoo and conditioner specifically designed for dyed hair.
- Reduce the frequency of hair washing to 2-3 times a week to prevent color fading.
- Use lukewarm or cool water when washing your hair, as hot water can open the hair cuticle and cause color loss.
- Apply a deep conditioning treatment once a week to keep your hair moisturized and healthy.
- Protect your hair from UV rays by using hair products with UV filters or wearing a hat when in direct sunlight.
- Minimize the use of heat styling tools, and always use a heat protectant when you do style your hair with heat.
- Consider using leave-in treatments or hair oils to add extra nourishment and shine to your dyed hair.
If you want to know more, click this link → <How to care colored hair? | 10 tips to help protect hair>.
