It goes without saying that smoking should be avoided by all people for a myriad of reasons, regardless of its effect on your headaches. Having said that, both active smoking, as well as second-hand smoke from cigarettes, cigars, and pipes can not only worsen existing headaches but can also trigger new onset headaches in many people.
This relationship exists for a few reasons. First, smoke inhalation increases inflammatory markers in the body, which in turn trigger pain sensitive structures leading to headache. In addition, nicotine, one of the components of tobacco, stimulates the blood vessels in the brain to narrow, when it is out of your system the blood vessels over-dilate which leads to rebound and withdrawal headaches. Finally, patients that suffer from migraines in particular, are often very sensitive to smell both during and between attacks, and being around the smell of smoke alone can often lead to a migraine attack. For many patients, by avoiding situations or places where smoking occurs, headaches may be avoided.
It should be mentioned that patients that suffer from migraines with aura are at a baseline increased risk of having a stroke in their lifetime. Smoking further increases that risk. Subsequently, while smoking is strongly advised against for all patients, patients with aura should be particularly mindful of their heightened stroke risk. One more reason to put down that cigarette!