When it comes to your own personal grooming, is there anything more satisfying than being crowned with a head of thick, shining hair? Do you divide your life into good hair days and bad ones? Does a bad hair day leave you depressed and lethargic while a good one propels you through glass ceilings. Guess what? You are not alone!
According to Hoovers® there are about 65,000 hair care salons in the United States with combined annual sales of about $19 billion! A small portion of these sales are for hair cuts, but most of this money is spent on… hair color.
If you are pregnant, planning to get pregnant or if you have a job in one of these salons, please read the following carefully. Over 20 million Americans, mostly women, are exposed to hair dyes each year. It has been estimated that at least 35 to 40% of all women in the United States and Europe use hair dyes. Solutions are applied either by a salon hairdresser or by individuals purchasing over the counter products.
According to the International Agency for Research on Cancer (IARC), concerns exist pertaining to the safety of these products. Why? Because some of the ingredients in hair dye are considered to be carcinogenic and teratogenic (causing malformation in fetuses). Reports of hairdressers having increased risk of spontaneous abortion, congenital malformations, childhood cancer and developmental problems exist. Older literature from the 1980’s report that men and women exposed to hair dyes in their occupations may experience increased risk of developing leukemia and cancers of the bladder, ovary, GI tract, and respiratory systems. Nasca, reported in the Journal of the NCI, that there is a higher risk of breast cancer in women that use hair dyes.
Pregnant women throughout the world who commonly use beauty products worry about the risk of exposure to themselves, and to their fetus, because of the potentially carcinogenic chemicals contained in these products. Many women are hesitant to use dyes during pregnancy due to fears regarding chemical use and absorption with risks to the fetus.
More concerning is the fact that many women are giving birth at later ages and therefore the use of hair dyes will become increasingly more popular. The combination of hormonal hair growth increase during pregnancy, and the increased need for coloring as a woman ages, obviously predicts an increased use of these products.
With all this in mind, I thought it would be a good idea to write an article that reviews the literature to date regarding the safety concerns of hair dyes so that you can make the right decision, for yourself, about whether or not to use these products. Overall conclusions, however, should be based upon the method of dye application (personal vs hairdresser), the colors used, the frequency of coloring, and the differences between varying product components available on the market.
How are hair dyes classified?
There are three classifications:
Chemical composition of the hair dye determines in which classification it is placed
Permanent dyes are the most prevalent and comprise about 75% of all hair dyes. They act by oxidation with hydrogen peroxide of dye precursors that permeate the hair fiber producing the color associated with the dye. Permanent hair dyes are commonly applied with a brush and by a hairdresser. Permanent hair dyes allow more dramatic changes in hair color. They do not wash out and they last until the hair grows or is cut.
Semi-permanent dyes comprise approximately 20% of all dyes and directly penetrate the hair cortex without the use of oxidizing agents. Generally the color lasts between 6 and 12 washings. These dyes, often applied by hand, are mostly used to cover gray or highlight the natural color, and are often purchased over the counter.
Temporary dyes, comprising about 5% of all hair dyes and are used for a single wash. This hair coloring is deposited on the cuticle layer of the hair and remains until shampooed out. It generally will not lighten hair but used to intensify natural color, tint hair another color, or add highlights to natural or tinted hair. It is also used to cover a limited amount of gray hair or eliminate yellowish shades from white or gray hair.
Which hair dye chemicals raise concerns in pregnancy?
Several reported studies have shown an increased risk of childhood brain tumors (CBT) associated with exposure to N-nitroso compounds, commonly found in hair dyes.
There are 2 broad classes of the N-nitroso compounds
Nitrosamides are unstable and do not require enzymatic activation and are inclined to tumor formation at the exposure site. In rats, they cross the placenta and are neurocarcinogens.
Nitrosamines, commonly found in tobacco smoke and beer, are considered carcinogenic agents.
Chemicals found in hair dyes are aromatic amines which get converted into nitrosamines. Nitrosamines, require this bioactivation and can initiate tumor formation in places at locations other than the initial exposure site. Hair dyes are considered NOC-related aromatic amines and contain ammonia based solutions, hydrogen peroxide, coal-tar dyes, and lead acetate. Many studies classify these agents as carcinogenic in animals when dosed orally because they alter DNA, but there exists « inadequate evidence » to determine carcinogenicity in humans when applied topically.
Other toxic chemicals found in hair dyes include phthalates, cobalt salts, formaldehyde releasing preservatives, lead acetate, nickel salts, 1,4-dioxane, diethanolamine/triethanolamine, and parabens.
How does exposure to the fetus occur when a pregnant woman uses hair dyes?
Exposure to the fetus occurs during routine use since many of the chemicals used are skin permeable. The particular characteristics of the dye products and their ability to penetrate skin influence their toxicity. Exposure can also occur via ocular, oral, or inhalation routes which can then cross the placenta and affect the fetus. Many of these chemicals can also be stored in body fat and also enter the mothers milk.
What type of toxicities have been described in pregnancy?
There have been many inconsistent results between use of hair dyes and various childhood cancers.
Some studies have shown an association between maternal hair dye and elevated risk of childhood cancer. The immature nervous system of the fetus has been found to be especially vulnerable to carcinogens and mutagens. If exposure occurs during the development of the nervous system during the first trimester, this may make the nervous system more susceptible to cancer and brain tumors.
Neuroblastoma, comprising about 6 to 10% of all childhood tumors in the developed world, is one of the most common cancers in children during the first year of life. A 3 fold increased risk was found in children of women exposed to hair dyes during pregnancy according to an article written by Kramer in the Journal of the National Cancer Institute in 1987. This increased risk is also confirmed by McCalls article in 2005 in Cancer Causes and Control. Wilms tumor, a cancer of the kidneys in children, had a 4 fold increased risk according to a study by Bunin in Cancer Research in 1987. Many of the chemicals used in 1987 in hair dyes have since been discontinued (2-4-diaminoanisole, 4-amino-2 nitrophenol, and HC Blue No.1) but other chemicals in the N-nitroso aromatic amines commonly used in hair dyes are still present which are carcinogenic in animals.
Other studies from the West Coast have found no association with hair dye use before or during pregnancy. (Holly in Pediatric Perinatal Epidemiology, 2002) One large study by Effird in Journal of Neuro-Oncology in 2005 also confirmed no statistically significant association between temporary, semi-permanent, or permanent hair dyes during pregnancy and childhood brain tumors, except for a 3 fold higher incidence of for brain tumor among Israeli children using semi-permanent hair color.
Do different types of hair dyes present different levels of risk?
Temporary dyes (includes semi-permanent) appear to have more toxicity than permanent dyes in pregnancy. Studies of scalp penetration of semi-permanent dyes compared to permanent dyes in both humans and monkeys found that semi-permanent dyes penetrated the scalp more than permanent dyes in both species. Unlike permanent dyes that contain oxidizing agents that allow the dye to irreversible bind to the hair shaft and therefore has lower skin absorption, semi permanent dyes achieve their coloring action via the use of various solvents (alcohols and ethylene glycol ethers) which penetrate the scalp more efficiently compared to permanent dyes. Also, greater skin contact occurs with semi-permanent dyes since they are applied as foam, rinse or surfactant solutions which tend to facilitate uptake by the skin. Semi-permanent hair coloring products also contain nitro derivatives of phenylenediamines or aminophenols, azo dyes and aminoanthraquinone dyes and N-nitroso compounds that have been shown to be transplacental neurocarcinogens in rodents.
Also, semi-permanent dyes are more likely applied by the person herself whereas permanent dyes were more likely applied by a hairdresser. With self-application there is more exposure to skin surface, such as hands, than if an outside person did the applications.
Smokers were also found to have greater toxicity than nonsmokers with dye use. Added exposure to nitrosamines and other carcinogens in cigarette smoke added to those carcinogens present in the hair dyes.
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