Nettle Clinical Evidence
Mittman P. Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis. 1990 Feb;56(1):44-7.
Can freeze-dried stinging nettles (Urtica dioica) help relieve symptoms in subjects with allergic rhinitis?
Stinging nettles grow in Asia, North Africa, Europe, and North America and have been used in folk medicine as early as the 10th century to treat rheumatism and arthritis. Since both of these diseases are characterized by an inflammatory response, might nettles treat allergy symptoms as well?
Human clinical intervention trial
Double-blind, randomized. Subjects kept a daily symptom diary and were assessed by the researchers after 1 week of treatment. Subjects took the stinging nettles when allergy symptoms appeared and rated their symptoms as dramatically improved, moderately improved, unchanged or worse 1 hour later.
98 subjects (69 completed) with allergic rhinitis
300 mg, at onset of symptoms, for 1 week
While diaries showed the nettle treatment to be only slightly more effective than placebo, global assessments indicated that nettles was significantly more effective than placebo. In fact, the treatment was found to be moderately or highly effective in 58% of the treatment group as compared to just 37% of the placebo group.
Stingling Nettle Mechanism of Action
Stinging nettle may also reduce production of histamine by inhibiting the action of histamine receptors and by preventing cells from releasing pro-inflammatory mediators. Nettle extract also inhibits the production of pro-inflammatory prostaglandins by reducing levels of COX-1 and COX-2, enzymes that cause pain and inflammation.