Every morning, millions of people use hair sprays, gels, and creams to style their hair with flat irons, curling irons, or blow dryers.
But a new study suggests this daily ritual may come with hidden dangers.
Engineers at Purdue University have found that heat-styling hair care products can release billions of tiny airborne particles—known as nanoparticles—that can travel deep into the lungs and potentially cause serious health problems.
The research team, led by assistant professor Nusrat Jung and her Ph.D. student Jianghui Liu, discovered that a 10 to 20-minute hair styling routine could expose a person to more than 10 billion nanoparticles.
That’s roughly the same amount of nanoparticle pollution you might inhale while standing in heavy highway traffic. Their findings were published in the journal Environmental Science & Technology.
“This is really concerning,” Jung said. “The number of nanoparticles released from regular hair care products when combined with heat was far greater than we ever expected.”
Nanoparticles are incredibly small—so small that thousands of them could fit across the width of a single human hair.
Because of their size, they can bypass the body’s natural defenses and travel deep into the lungs, where they may trigger inflammation, breathing problems, and even cognitive decline.
Until now, there had been no real-world measurements of how many nanoparticles are created during typical hair styling routines inside homes.
Jung’s team filled that gap by studying what happens when store-bought hair products are used with high heat in a residential setting. Using advanced instruments similar to those employed for measuring car exhaust, they tracked the formation of nanoparticles in real time. The results were startling.
The biggest culprit turned out to be a common ingredient called decamethylcyclopentasiloxane, or D5 siloxane, often listed among the first ingredients in many sprays, gels, and creams. When exposed to temperatures above 300 degrees Fahrenheit, this chemical and others quickly evaporate, then reform into massive clouds of new nanoparticles. Most of these particles were smaller than 100 nanometers, small enough to be inhaled and absorbed into the bloodstream.
D5 siloxane is part of a chemical family called cyclic siloxanes, which are valued in cosmetics for their smooth feel and stability under heat. But the European Chemicals Agency classifies D5 as “very persistent” and “very bioaccumulative,” meaning it can build up in living organisms and the environment. Animal studies have linked it to liver, respiratory, and nervous system problems, though its long-term impact on humans is still poorly understood.
When the Purdue team measured how these particles spread through the body, they found that the deepest part of the lungs, known as the pulmonary region, received the highest dose. This could increase the risk of chronic respiratory illness. “Our modeling showed that more than 10 billion nanoparticles could be deposited in the lungs from just one styling session,” Liu said.
The findings highlight a hidden but significant source of indoor air pollution. Everyday beauty routines, especially those involving heat, may expose people to higher risks than previously realized.
So what can be done? The researchers recommend avoiding heated styling products whenever possible, especially sprays and “leave-on” formulations designed to resist heat. If avoiding them entirely isn’t realistic, the next best option is to improve ventilation. Using a bathroom exhaust fan, opening windows, or using an air purifier during styling can help reduce exposure. Even without heat, products like sprays and gels release volatile chemicals, so ventilation is still important.
The team conducted their experiments in Purdue’s “zEDGE” laboratory, a specially designed tiny house built to study indoor air pollution. Volunteers brought their own styling tools and products to replicate realistic routines.
Sophisticated instruments tracked the release and decay of nanoparticles second by second. The researchers also tested how factors such as hair length, styling tool temperature, and product type affected emissions.
This groundbreaking study is just the beginning. Jung explained that more work is needed to identify the exact chemical makeup of the particles and to study their effects on human health in detail. “Future research should focus on detecting particles down to a single nanometer and analyzing their chemistry,” she said.
For now, the message is clear: heat-styling with common hair care products may expose people to unexpected health risks.
Something as routine as curling your hair in the morning could quietly be filling your lungs with billions of microscopic pollutants. he researchers hope their work will raise awareness and encourage people to take small steps—like ventilating their bathroom—that could protect their long-term health.
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