Urticaria is a vasoactive condition that is caused by vasoactive mediators. These mediators are released from activated mast cells triggering an immune response. The immune response results in wheals or hives that appear on skin within 6-8 hours and disappear within 48 hours. But the symptoms can recur several weeks later also.

The association between urticaria and infection had been reported earlier. There is evidence that suggests that urticaria can be induced by several infections, such as virus and bacterial infections other than food and drugs. Pathogenically, Mycoplasma pneumoniae (MP) infection might be related to urticaria.

A nationwide population-based cohort study was conducted from 1997 to 2013, which explored the association between MP infection and urticaria. Overall, 1,175 patients were included in the study group, and 2,350 patients in the control group. Multivariate Cox regression analysis was done to assess the adjusted hazard ratio (aHR) for urticaria.

The study result revealed that 254 patients with new-onset urticaria were involved in the study group and 465 incident cases were seen in the control group. The occurrence rates (per 100,000 person-months) of urticaria were 37.2 and 32.5 in the study and control groups, respectively. The relative risk was 1.1 demonstrating no significant correlation between MP and urticaria.

The multivariate analysis thus showed that the risk of urticaria with MP infection had no statistically significant difference as compared to the control group. But, the urticaria in MP-infected patients who were aged between 20 and 59 years were found to have increased risk prior to a diagnosis.

Source: Yong SB, Yeh WC, Wu HJ, et al. Impact of mycoplasma pneumonia infection on urticaria: A nationwide, population-based retrospective cohort study in Taiwan. PLoS One. 2019;14(12):e0226759. Published 2019 Dec 20. doi:10.1371/journal.pone.0226759