Understanding the Relationship Between Smoking and Hidradenitis Suppurativa.

Hidradenitis suppurativa (HS) is a chronic skin disease affecting hair follicles in intertriginous areas, characterized by deep, recurrent, painful nodules and abscesses, fistulae, sinus tracts, and scarring. With a prevalence of 1-4%, HS is not an uncommon disease. Several risk factors have been linked with the development of HS, such as genetic predisposition, smoking, and obesity, leading to the hypothesis that HS develops as a result of environmental triggers in a genetically susceptible individual. Smoking has been recognized as one of the environmental factors with the most impact on HS. This review aims to provide a comprehensive and holistic view on how smoking habits affect the incidence, severity, treatment, and pathophysiology of HS. A growing body of published literature has reported the association between smoking and HS, despite limitations in proving the causal relationship due to the retrospective design of the available studies. There is a consensus that patients with HS who are active smokers have a higher number of affected body areas than patients with HS who do not smoke or have stopped smoking. Similarly, it is recommended for patients with HS to discontinue tobacco use because of its association with weaker treatment response. Studies on the pathophysiological mechanism of smoking on the skin show that tobacco smoke with many of its chemicals as well as nicotine promote the proinflammatory cytokines found in HS lesions, activate the nicotinic acetylcholine (nAChRs) and aryl hydrocarbon receptors (AHRs), and further suppress Notch signaling pathway.