Smoking is a widespread habit with numerous health risks, impacting several body systems and leading to various diseases. While it's widely associated with respiratory and cardiovascular diseases, smoking also triggers inflammatory reactions due to its effect on the immune system. The thousands of chemicals in tobacco, like nicotine and polycyclic aromatic hydrocarbons, are harmful and have been classified as antigenic, cytotoxic, mutagenic, and even cancer-causing.

In the realm of autoimmune skin conditions, smoking's influence varies. It worsens conditions like psoriasis, palmoplantar pustulosis, and hidradenitis suppurativa. Conversely, some diseases like pemphigus vulgaris and Behçet’s disease show decreased association with smoking. For instance, Behçet’s disease oral lesions tend to emerge after quitting smoking, suggesting nicotine might have some protective effects. However, this isn't consistent across all studies, and other aspects of Behçet’s disease are exacerbated by smoking.

Smoking has also been linked to poorer wound healing and accelerated skin aging. On the other hand, there are cases where smoking seems to offer protective effects against certain conditions. For example, those who smoke or used to smoke have a lower incidence of pemphigus vulgaris, and stopping smoking can lead to the onset of aphthous ulcers. Moreover, conditions like Parkinson’s disease and ulcerative colitis show reduced association with smoking, though the exact reasons remain unclear.

While smoking introduces many reactive oxygen species (ROS) harmful to health, it also contains compounds that inhibit monoamine oxidase (MAO) activity, thereby reducing some ROS production. Some research even indicates smokers have lesser MAO activity than those who've never smoked. Nicotine has also been noted to have some antioxidant properties.

In the specific case of vitiligo, this nationwide study by Ji Hyun Lee et al found that current smokers had a reduced risk, contrary to initial expectations. Since vitiligo involves the loss of skin pigmentation due to melanocyte destruction, and oxidative stress plays a role in this, the expected outcome was that smoking would increase the risk. Elevated ROS levels, higher MAO activity, and lower antioxidant levels are often found in vitiligo patients. It's hypothesized that the reduced risk of vitiligo in smokers could be due to tobacco's inhibitory effects on MAO. Still, the precise mechanism warrants further investigation.

Nevertheless, given the overarching detrimental effects of smoking and the lack of clear benefits concerning vitiligo, it's not advisable to consider smoking as a preventive or therapeutic measure for vitiligo.