When you smoke, thousands of toxic substances enter your bloodstream through your lungs, where they can affect every part of your body. This includes your hair follicles.
Smoking restricts the flow of blood to your follicles, resulting in premature aging in your hair. When you smoke, you are likely to see grey hairs far earlier in life than you otherwise would. Sometimes your hair will begin to take on a yellow hue, due to the tar and nicotine of your cigarettes. Your hair will also likely be more brittle, prone to breakage and falling out.
Another effect of smoking is that it increases your body’s production of a hormone known as DHT. This hormone is known to contribute to hair loss. This is why smokers are known to have thinner hair than their non-smoking friends, and occasionally experience premature balding.
Even the smell of smoke can affect your hair. This smell easily adheres to your skin and hair, causing you to carry the stale, musty odor of smoke with you long after you are done smoking.