Unbeknown to many parents, a few hair products - especially some marketed to black people - contain small amounts of hormones that could cause premature sexua| development in girls.

The evidence that hair products containing oestrogens cause premature puberty is largely circumstantial, and the case is still unproven. But Ella Toombs, acting director for the Office of Cosmetics and Colors at the US Food and Drug Administration, told New Scientist: "No amount [of oestrogen] is considered safe and can be included in an over-the-counter product."

Under FDA regulations, over-the-counter products containing hormones are drugs, and thus require specific approval. However, there appears to be a grey area regarding products marketed before 1994. The FDA failed to respond to a request to clarify the position. At least five companies are still making hormone-containing hair products, a source within the industry - who preferred not to be named - told New Scientist.

Throughout the West, girls are tending to reach puberty earlier. This has been blamed on everything from improved diet to environmental contaminants. But African-American girls are developing even earlier than their white counterparts. About half of black girls in the US begin developing breasts or pubic hair by age eight, compared with just 15 per cent of white girls, one study has found. In Africa, girls enter puberty much later, regardless of their socioeconomic status.

"Placenta, hormones or estrogen" 

That big discrepancy may be explained, at least in part, by the more frequent use of hormone-containing hair products among African Americans, says Chandra Tiwary, former chief of paediatric endocrinology at Brooke Army Medical Center in Texas. "I believe that the frequency of sexua| precocity can be reduced simply if children do not use those hair products," he says.

The products are sold as shampoos or treatments to deep-condition dry, brittle hair. The labels usually state that they contain placenta, hormones or "estrogen", although not all products that make such claims contain active hormones. While New Scientist's inquiries suggest such products are no longer sold in Europe, many are still available worldwide over the Internet.

And they remain popular among African Americans. A small study published earlier this year by Su-Ting Li of the Child Health Institute in Seattle suggests that nearly half of African-American parents use such products, and that most also use them on their children.

For other ethnic groups the figure is under 10 per cent. Tiwary told New Scientist that he has carried out a bigger, as yet unpublished, survey of 2000 households that confirms these findings.

In 1998 Tiwary, now retired, published a study of four girls - including a 14-month-old - who developed breasts or pubic hair months after beginning to use such products. The symptoms started to disappear when they stopped using them. The year before, he published a study showing that some of the products used by his patients contained up to four milligrams of oestradiol per 100 grams. Others contained up to two grams of oestriol per 100 grams.

Readily absorbed 

B&B Super Gro, for example, which was marketed before 1994 and is still on sale in the US and claims to be "rich in hormones", was found to contain 1.6 grams of oestriol per 100 grams. While the levels of oestriol in the products were much higher, oestradiol is a far more potent form of oestrogen.

There is no doubt that oestrogens are readily absorbed through the skin--hormone therapy is often delivered via patches. Long-term exposure to these doses could cause premature puberty, Tiwary believes.

And his studies are not the only ones hinting at a possible effect. Anecdotal reports in scientific papers going back to 1982 describe early puberty in children after use of hair treatments, as well as certain ointments. Tiwary notified the FDA of his concerns in 1994, but says he never received a reply.

The evidence that oestrogen-containing hair products cause early puberty remains limited. There are too many other suspect substances to pin the blame on them without further studies.

"A person isn't exposed to just one chemical, but rather a mix of many," says Julia Brody, director of the Silent Spring Institute in Massachusetts, a non-profit organisation that looks at the environment and women's health. "There is an increasing awareness that hormonally active compounds are present in cosmetic products."

Some cosmetics contain estrogens, representing a potential source of exogenous estrogen for children. In contrast to pharmaceutical preparations, the Food and Drug Administration (Rockville, Md) does not regulate cosmetics containing less than 10 000 IU of estrogen per ounce, only stating that the label should direct consumers to limit the amount of product used to less than 20 000 IU/mo.1, 2 A therapeutic dose of oral ethinyl estradiol for hormone-replacement therapy in adults is 0.02 to 0.05 mg/d (4000-10 000 IU/d). An equivalent therapeutic transdermal estradiol dose for hormone-replacement therapy is 0.05 mg/d.

Two case series suggest that exogenous hormones found in hair products may be associated with early pubertal development in African American girls.2, 3 In 3 of 4 cases, pubertal characteristics regressed on discontinuation of these products.³ Patterns of use of hormone-containing hair products (HCHPs) are unknown. One survey of parents at 4 southern US Army hospital clinics revealed that 64% of African American parents and 6.9% of European-American parents used HCHPs, and 55.5% of those parents used them on their children.4

We estimated the prevalence of HCHP use among different ethnic groups in an urban clinic population, which included immigrant populations. We surveyed parents with children younger than 10 years attending 3 Seattle, Wash, pediatric clinics between November 1999 and January 2000. Color copies of product labels of HCHPs were used as pictorial guides. Age, sex, and frequency of exposure to HCHPs were documented to better understand whether prepubertal children were regularly exposed to these products.

A total of 130 parents were surveyed. Race/ethnicity was reported as follows: 25% African American, 25% African immigrant, 20% European American, 12% Asian/Pacific Islander, 11% Hispanic, and 6% other/unspecified. Of the 247 children reported, 55% were girls, 41% were boys, and 4% did not specify sex. Age group distribution was as follows: 8%, younger than 1 year; 48%, 1 to 5 years; 26%, 6 to 9 years; and 19%, 10 to 18 years.

The use of HCHPs was reported by 21% (27/130) of respondents (Table 1). More African American parents (45%) used HCHP than parents of all other races/ethnicities (² = 16.4; P<.001), including African immigrant parents (12%). Eighty-five percent of parents using HCHPs also used these products on their children, including children younger than 5 years. Most families (65%) who used HCHPs on their children used them only occasionally but a third of families reported regular use. One limitation of this study is that we were unable to quantitate the exact dose or absorption of these products.

A recent study revealed that girls are developing at an earlier age than has been observed previously and there is a significant difference between mean age of onset of puberty in European American compared with African American girls.5, 6 Since it is unknown why African American girls are entering puberty at an earlier age than their European American or African counterparts, it is possible that the use of HCHPs may contribute to earlier onset of puberty in this population. More research is needed to ascertain whether an association exists between the use of HCHPs and the early onset of puberty.