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

Randomised controlled trials (RCTs) and quasi-experimental studies of herbal medicines, given orally or topically, for the treatment of asthma or experimentally induced asthma in children or adults were eligible for this review. Herbal medicines were defined as the use of any plant part or combination of plant parts. Traditional Chinese medicine herbs and exclusively synthetic products were excluded from the review. Studies were required to report effectiveness via pulmonary function tests or symptom scores.

The included studies for this evaluated a variety of Ayurvedic (traditional Indian medicines) and non-Ayurvedic medicines. The Comparisons included placebo, standard conventional medicine or different doses of the intervention. The populations varied widely, studies included healthy volunteers, patients with stable or asymptomatic asthma, bronchial asthma and allergic or chronic bronchitis. Where reported, age ranged from five to 79 years and, where reported, there seemed to be a greater number of males. The pulmonary function tests related to expiratory volume and flow, vital capacity and breath capacity. Study duration ranged from three days to one year.

https://www.ncbi.nlm.nih.gov/books/NBK74235/?report=printable