Impact of mycoplasma pneumonia infection on urticaria: A nationwide, population-based retrospective cohort study in Taiwan

Mycoplasma pneumonia (MP) infection might be pathogenically closely related to urticaria. This study is a nationwide population-based cohort study from 1997 to 2013, which investigated the association between MP infection and urticaria in Taiwan. A total of 1,175 patients were included for the study group, and 2,350 for the control group. Multivariate Cox regression analysis was performed to estimate the adjusted hazard ratio (aHR) for urticaria. Result showed that 254 patients with new-onset urticaria were involved in the study group and 465 incident cases in the control group. The incidence rates (per 100,000 person-months) of urticaria were 37.2 and 32.5 in the study and control groups, respectively. The relative risk is 1.1 (95% CI = 1.0–1.3) indicating no significant correlation between MP and urticaria. The multivariate analysis revealed that the risk of urticaria with MP infection (aHR = 1.1, P = 0.1058) had no statistically significance difference compared to the control group. However, the risk of urticaria in MP-infected patients aged between 20 and 59 years old was found to have increased (aHR = 1.6, 95% CI = 1.1–2.2) prior to a diagnosis.