Efficacy, chemistry and pharmacology of chinese herbal medicine for allergic rhinitis.

An extensive literature search identified six randomized controlled clinical trials in which the efficacy of Chinese herbal medicine had been investigated for the treatment of allergic rhinitis. Although four of these trials had methodological flaws, the therapeutic outcomes of all six have been reviewed. One of two trials considered to be of high quality was concerned with the treatment of seasonal allergic rhinitis and the other with perennial allergic rhinitis. It is considered that all six studies demonstrated various degrees of alleviation of the symptoms of allergic rhinitis. No serious side effects were reported in any of the trials. A number of the herbs in the Chinese herbal formulae used in the trials, and/or their constituent compounds have been reported to possess anti-allergic, anti-inflammatory or immune modulation activity. Such actions include inhibition of the release or action of mast cell mediators such as histamine, inhibition of inflammation induced by chemical agents, and modulation of serum IgE levels or of lymphocyte and/or macrophage activity. An aqueous, unresolved extract of the herbal formula used in one of the six trials has been reported to exhibit a range of pharmacological actions relevant to the treatment of allergic rhinitis. Essential oils, lignans, flavonoids and saponins are chemical classes that are frequently represented in individual herbs of the six Chinese herbal formulae used in the trials. The chemical structures characterising these classes of compound and the pharmacological actions of these and other constituents of the herbs, relevant to allergic rhinitis, have been reviewed.