Smoking habits in psoriasis: a case control study.

Summary We have examined smoking habits in 108 patients with psoriasis, including some with palmoplantar distribution, and compared the results with matched controls from the community. There was a significant association between psoriasis, current smoking status(OR=2.7, 95% CI 1.44-5.42, P<0.01) and smoking habits prior to the onset of disease(OR=3.75, 95% CI 1.68-9.47, P<0.001). There was also a marked dose-response relationship; the relative risk of psoriasis in those currently smoking more than 20 cigarettes/day was significantly elevated(OR=5.3, 95% CI 2.1–13.0, P<0.001). Separate analysis of patients without palmoplantar distribution of psoriasis showed a significant association with smoking prior to onset of psoriasis(OR=3.6, 95% CI 1.5–9.8, P<0.001). Smoking may play a role in the aetiology of this common skin disorder.