CRD Summary: This review of Ayurvedic (traditional Indian medicines) and non-Ayurvedic herbs for asthma concluded that herbs may be a useful treatment despite the limited evidence. The conclusions are likely to be reliable but should be considered with caution given the methodological limitations of the review.

CRD Commentary: This review addressed a broad question with broad inclusion criteria. The searches may not have fully addressed the grey literature leading to potential publication bias, and omitted the main complementary/alternative medicine database (AMED). Language bias is likely given the restriction to English language papers and, with the focus on Ayurvedic (Indian) herbs, the review may have omitted relevant studies. The processes of study selection and data extraction were not described, which making it difficult to ensure that reviewer error/bias was sufficiently addressed. Quality was assessed using several complex scales and performed in duplicate but the presentation of overall summary scores may have resulted in the loss of useful details. The heterogeneous studies were appropriately discussed within a narrative synthesis, although this often failed to summarise the overall results. As well as discussing in terms of type of herb, it may have been useful to see the results presented according to type of asthma. The majority of studies reported some positive benefits of herbs in pulmonary function tests, and therefore the authors' conclusion seems reliable. However, the magnitude of these benefits is not known and often applied to particular outcomes that varied across studies.