Nicotine quickly enters your bloodstream. Your liver then breaks down nicotine into several byproducts, primarily cotinine. Depending on what you're testing, such as a blood, urine, saliva, or hair ...

Even one cigarette can affect the body shortly after the first puff.

Sarah covers how industries like food and tobacco affect Americans’ bodies and minds. Her interests include ultra-processed foods; smoke-free tobacco; and wellness trends like perimenopause products ...

As a physician, I witness the subtle signs of nicotine use daily. I walk through clouds of sweet-smelling smoke from vape pens as I enter the grocery store. At traffic lights, I glance over to see ...