Lachnospira is a signature of antihistamine efficacy in chronic spontaneous urticaria.

Chronic spontaneous urticaria (CSU) is a mast cell-driven disease with many advances in its aetiology and pathogenesis over the past years. The main treatment of CSU is oral second-generation antihistamines. However, only an average of 50% of CSU patients responded adequately to conventional or quadruple doses of non-sedative antihistamines. Meanwhile, gut microbiota can affect the efficacy of drugs. The purpose of this study was to investigate the relationship between gut microbiota and the efficacy of antihistamines in patients with CSU. The patients with CSU were divided into responders and non-responders according to the efficacy of antihistamine monotherapy. The gut microbiota of faecal samples from 15 responders and 15 non-responders was detected by 16S rDNA sequencing, and the differential bacterial species between the two groups were verified by quantitative polymerase chain reaction (qPCR). Additional faecal samples from 30 responders and 30 non-responders were used as an extended cohort to further verify the above differential bacterial species by qPCR. Lachnospiraceae and its subordinate taxa were found to be the main differences in gut microbiota between responders and non-responders. The abundance of Lachnospira in responders was higher than that in non-responders. Lachnospira exhibits moderate diagnostic value in evaluating the efficacy of antihistamine. Lachnospira is a signature for predicting the efficacy of antihistamine in patients with CSU.