Calms the central nervous system. Vervain has been useful to herbal healers for many centuries of recorded history. Vervain's healing properties are attributed primarily to its bitter and stimulating effect on the liver and other organs, as well as its relaxing effect on the nervous system. Blue vervain is a herbal remedy that relieves respiratory and liver congestion, lower fevers, eases coughs and colds, cleanses toxins, calms the nerves and acts as a general tonic that produces an overall feeling of well-being.