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Thirdhand Smoke Can Trigger Skin Diseases, Study Finds

Imagine if cigarette smoke and dust had a baby. And it could trigger psoriasis.


Dr. Katie Spalding

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory.

Freelance Writer

A no smoking sign
No smoking (retrospectively) Image: Mr.Louis/Shutterstock

If you don’t know by now that smoking is bad for you, then we can only assume you’re a time traveler from 1936 sent here to warn us all about the looming Nazi threat in Europe (don’t worry: we won.) 

But what we’re still getting to grips with is just how bad for you it is. A new study led by researchers at the University of California, Riverside, has found harmful effects from not just first or second-hand smoke, but thirdhand smoke – all those pollutants and chemicals that are expelled from cigarette smoke and settle indefinitely on surfaces like our walls, carpets, curtains, clothes, furniture, and so much more that surrounds us every day.


“We found exposure of human skin to THS [third-hand smoke] initiates mechanisms of inflammatory skin disease,” said Shane Sakamaki-Ching, a doctor of cell, molecular, and developmental biology, and first author of the paper, in a statement on the findings. “Alarmingly, acute dermal exposure to THS mimics the harmful effects of cigarette smoking.”

The study – the first to look at humans exposed dermally to thirdhand smoke – involved 10 healthy non-smokers wearing clothing impregnated with either filtered air or third-hand smoke particles. The investigation lasted three hours total, during which time participants would either walk or run on a treadmill for at least 15 minutes per hour – this would make them sweat, and thereby increase the levels of third-hand smoke potentially taken in through the skin. 

Blood and urine samples were collected at regular intervals from all participants, which were measured for protein changes and markers of oxidative stress – hints that the third-hand smoke may have caused cell or tissue damage.

“We found acute THS exposure caused elevation of urinary biomarkers of oxidative damage to DNA, lipids, and proteins, and these biomarkers remained high after the exposure stopped,” said Sakamaki-Ching, now a research scientist at Kite Pharma in California. “Cigarette smokers show the same elevation in these biomarkers.”


Being exposed to third-hand smoke, the study revealed, elevates specific biomarkers associated with skin diseases like contact dermatitis and psoriasis – which makes sense: the organ most likely to come into contact with THS is your skin, and so it probably receives the biggest exposure to the harmful pollutants contained within it. 

Even more worrying than that, though, is the “oxidative harm” recorded in the study, which “could lead to other diseases, such as cancer, heart disease, and atherosclerosis,” Sakamaki-Ching said. 

All of which, when you consider how persistent and unpredictable third-hand smoke can be, is a big potential problem. “There is a general lack of knowledge of human health responses to THS exposure,” said Prue Talbot, a professor of cell biology at UC Riverside, and corresponding author of the study. 

“If you buy a used car previously owned by a smoker, you are putting yourself at some health risk,” she pointed out. “If you go to a casino that allows smoking, you are exposing your skin to THS. The same applies to staying in a hotel room that was previously occupied by a smoker.”


And all that from just three hours’ investigation – although the researchers plan to investigate larger populations exposed for longer periods in the future. And lest you think e-cigarette smokers are being forgotten, fear not: the team’s next project is to take a look at which residues are left by these less-deadly death sticks.

“This [study] underscores the idea that dermal exposure to THS could lead to molecular initiation of inflammation-induced skin diseases,” Sakamaki-Ching said. 

“Our findings can help physicians in diagnosing patients exposed to THS and help develop regulatory policies dealing with remediation of indoor environments contaminated with THS.” 

The study can be found in the journal eBioMedicine, part of The Lancet family of journals.


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