Now experts are using these findings to further investigate the danger of using chemical products on the body.
The study was conducted by researchers at the Rutgers School of Public Health and Rutgers Cancer Institute of New Jersey.
Experts asked more than 4,000 black and white women in the New Jersey and New York area their habits of dying, relaxing or using deep conditioning creams.
Researchers then examined the study participants' medical history to see if these products elevated the risk of breast cancer.
Black women who used dark hair dye had an overall 51 per cent greater risk of the cancer.
They also had a 72 per cent increased risk of developing estrogen receptor positive breast cancer, which is the most common type of the disease.
It is not yet understood why dark hair dyes in particular pose a risk.
White women who used chemical relaxers/straighteners had a 74 per cent increase in risk.
In general, black women have an 11 per cent chance of developing the disease and white women have a 13 per cent chance.
Professor and study lead author Adana Llanos said: "One hypothesis is that the chemical composition of hair products marketed for and used among whites may differ from the products marketed for use by African-Americans."
The researchers speculated this increase may have something to do with DNA damage or
the body absorbing the chemicals used to change the hair.
Llanos added: "More research is needed to determine specifically which compounds and chemicals are dangerous and even which specific consumer products and brands contain those chemicals.
"Just because we found these associations doesn't mean that if you dye your hair dark, or any colour, you're going to get breast cancer.
"But at the same time, the study points to something else we should be mindful of."
Experts claimed in March breast cancer was linked to hair dye and hormonal contraception.
A Finnish study found being exposed to carcinogenics in the dyes was linked to a 23 per cent chance of getting the disease.
Users of birth control methods such as the combined Pill and IUS coils could also face the same plight.
Post-menopausal women fitted with the latter have a 52 percent greater chance of developing breast cancer.
And there is a 32 percent increased risk for those who use the former hormonal-based contraceptive, the researchers claimed.
The findings add to the growing body of evidence that progesterone-based birth control
methods are a risk factor of breast cancer.
DANGER CHEMICALS IN HAIR DYE
• PPD (para-phenylenediamine)
This chemical is found in dark hair dyes - concentrations of up to six per cent are legal - and is easily absorbed through the skin on the scalp and the hands.
• Lawsone
A naturally occurring chemical, found in henna at concentrations of between one and two per cent, but, none the less, one that is toxic, and can affect the kidneys, blood supply and stomach.
• Ammoniated mercury
These have a bleaching action which enhances color in the hair, but they can cause allergic reactions.
• Peroxide
This breaks down the melanin in the shaft to lighten the hair. Can cause allergic reactions and can irritate the skin and lungs, but is not toxic.
• Nonylphenol or octylphenol
Members of a group of chemicals which studies suggest are hormone disrupters and bioaccumulators. This means they can build up faster in body fat than they can be broken down.
• Aniline dyes
Derived from coal tar and used in semi-permanent dyes. Can irritate eyes, skin and mucous membranes, or cause allergic reactions.
