The drug damages what are known as endothelial cells, which line the inside of your blood vessels, and that keeps them from functioning as well as they should, says Christopher Snyder , MD, the chief of paediatric cardiology at University Hospitals Rainbow Babies & Children’s Hospital. Nicotine also affects your platelets, tiny cells that helpblood clot. “This makes it hard for blood to get to the distal parts of the bodies, such as the fingertips, and it puts pressure on those blood vessels,” he explains.