Hormone-disrupting chemicals found in cosmetics could explain an “alarming” trend of girls starting to have periods earlier than ever before.
A US government-backed study has found that these chemicals (found in detergents, perfumes and cosmetics) block and mimic the production of hormones responsible for the onset of puberty in girls, such as those that trigger ovulation.
This would explain why the average age of puberty has decreased since the 1990s, particularly in girls than in boys.
The chemicals are responsible for the sweet, musky smell of many perfumes, and are also found in asthma and smoking cessation medications.
NIH researchers have found that exposure to chemicals may trigger early puberty in girls, which is on the rise in the United States.
The findings also come at a time when girls are starting to use makeup and perfume at younger ages, with recent research finding that eight out of ten Children aged nine to eleven in the US who use some type of beauty product.
Researchers at the National Institutes of Health (NIH) exposed lab-grown human cells and zebrafish cells to 10,000 different environmental contributors.
Zebrafish are commonly used for studies like this because they share several genetic similarities with humans and other mammals.
They found that a fragrance called ambrette musk and drugs called cholinergic agonists could alter, mimic, or block the effect of the hormones.
Musk ambrette is a sweet, musky, seed-like scent that is derived from a yellow flower. Although its use is restricted in the U.S., it can still be found in small quantities in various perfumes sold to young girls on online marketplaces such as Amazon and Etsy.
Cholinergic agonists, on the other hand, are drugs used primarily to treat tobacco addiction, COPD and asthma.
“There has been an alarming trend toward earlier puberty in girls, suggesting the influence of an environmental factor,” the study authors wrote.
Obesity, sedentary lifestyle and stress have been previously mentioned as possible explanations.
The girls previously told DailyMail.com that the phenomenon is not only “mortifying” at school and at home, but can also be confusing and cause them to miss out on holidays and other social activities.
Early puberty in girls has been linked to complications such as increased risk of obesity, heart disease, breast cancer and psychological problems.
Menstruation typically begins around age 12, but study author Dr. Natalie Shaw, a neuroendocrinologist at the National Institute of Environmental Health Sciences (NIEHS), said that in recent decades, girls on average have tended to start earlier.
In some cases, girls as young as six have started menstruating before noticing any other signs of puberty.
Large-scale studies in the 1990s confirmed the average age at which girls begin to develop breasts, a sign of puberty that often begins before the start of the first period, at around age ten.
This was about a year earlier than scientists previously thought, and further studies They have confirmed that since the 1970s, the average age of onset of puberty has decreased by approximately three months per decade in girls.
This trend suggests that something in our environment is playing a role, the study authors wrote.
To investigate this, a group of doctors at NIEHS, a branch of the NIH, analyzed a database of chemicals and prescriptions that might have an effect on hormones.
Their findings were published in the journal Journal of endocrinology.
Doctors have not been able to identify a single or even a handful of causes for precocious puberty, although experts have told DailyMail.com that some underlying factors include obesity, stress and genetics.
Specifically, they analyzed molecules called endocrine disruptors (EDCs), substances that mimic, block or interfere with the natural flow of hormones. These control puberty, stress and development. according to NIEHS.
EDCs are found everywhere – from flame retardants to so-called forever chemicals to plastics – so the researchers included 10,000 potential targets in their investigation.
They focused on two: the musk ambrette and drugs called cholinergic agonists.
Ambrette musk has been used over the years to provide a pleasant smell to detergents, perfumes and makeup, as well as in chewing gum, candy and beverages, according to International Agency for Research on Cancer.
Its use is restricted in the United States, the European Union and Canada. The FDA has removed it from the list of fragrances “generally recognized as safe” and widely used in the country.
The watchdog group Environmental Working Group (EWG) says there is “strong” evidence that ambrette musk causes skin allergies.
However, the authors write, ambrette musk has still been detected in some water and fragrance sources, including several on online marketplaces such as Amazon and Etsy.
Cholinergic agonists are a type of prescription medication, such as Chantix, that is used to help people stop smoking. “Children are less likely to encounter cholinergic agonists in their daily lives,” the authors wrote.
However, two asthma medications called ipratropium and tiotropium are also cholinergic agonists.
When the scientists applied both chemicals to human cells grown in the lab and to live zebrafish, they activated cells that control puberty, called musGnRh neurons.
This, they write, suggests that exposure to these EDCs could be causing the earlier onset of puberty.
“This study suggests that, as a precaution, it is important for parents to only use personal care products on their children that are federally regulated,” said Dr. Shaw.