That's the question people ask all the time...is nicotine bad for you? That's like asking an alcoholic if going to a tavern is bad for them. Well no, not in and of itself, but yes because it leads to another drink. Sadly, that shouldn't be the question asked. People should be more concerned with the broader question, is smoking bad for you. However, since you asked, we'll try to answer the best we can.
In general terms, nicotine in and of itself, is probably no worse than the cholesterol that is found in the fried egg sandwich you had earlier today; let me explain.
Nicotine and the Brain
Nicotine and the brain do a dance. The brain develops an affinity or an attraction for nicotine and decides it can't function normally without it. So, nicotine negotiates a friendly little pact and the brain is hooked. Once this link has taken hold, nicotine brings it's friends along with it in each cigarette smoked. These friends are certainly bad for you.
These are the carcinogens and irritants which cause disease, such as lung cancer, COPD or any of the other horrible and devastating diseases related to tobacco products. These nasty ingredients would never have access to your physiology if it weren't for the addictive properties of nicotine and the brain.
Is nicotine bad for you, well, I guess it depends on how you look at it. But the overall answer shared by most medical scientists and researchers is "yes, it is indirectly bad for you". Because it is more about nicotine becoming a gateway for disease. Obviously, it's the subsequent addiction to nicotine which serves as the primary answer to the question. Addiction is never healthy. Nicotine addiction only ever leads to disease. Nicotine and the brain should not be friends.
Not to sound like a broken record, but the question "Is nicotine bad for you?" should be changed to "Is smoking bad for you?" and I think we all know the answer to that question.