The third valid concern of many professionals is the lack of standardisation of doses and constituent content in the various products. Urtica dioica has been suggested as a treatment for allergic rhinitis and asthma. One component, scopoletin, has shown anti-inflammatory actions in laboratory studies. However, there are no clinical data to support efficacy or use in these disorders. It does possess diuretic actions and use may cause electrolyte imbalance and contact dermatitis.
Rodent studies indicate that extracts possess anti-inflammatory properties.
However there are no human studies to support any efficacy in the treatment of asthma. Side effects include cholinergic overload, contact dermatitis, and gastro-intestinal upset. The FDA has ruled that extracts are neither safe nor effective for treating asthma. Numerous constituents are found in extracts, with the primary component of benefit identified as parthenolide, a sesquiterpene lactone. Mechanistically, this has been shown to inhibit serotonin release.