Foxglove leaf was once widely used in herbal remedies despite its high toxicity - it can cause vomiting, diarrhoea and, if the dose is high enough, cardiac arrest. However, those suffering from dropsy, if they did not die of the treatment, often showed a marked improvement. Dropsy was the name once used for excessive fluid retention in the body tissues, the most likely cause being heart failure.

In 1775 William Withering, a young doctor practising in rural Shropshire, was asked to investigate a herbal remedy used by a ‘wise woman’ in the successful treatment of dropsy. The remedy contained at least twenty herbs, but Withering was quick to deduce that its most active ingredient was foxglove. In the years that followed, Withering carried out painstaking research into the effects of the plant, first on some unfortunate turkeys, and later, more cautiously, on his own patients. In 1785 he published his findings in his book entitled An Account of the Foxglove.

Foxglove leaves contain chemicals called cardiac glycosides, responsible for slowing and strengthening the action of the heart. They are still used today as a source of the drug digoxin, though nowadays the European species Digitalis lanatais more often used.

Richard Mabey has suggested that Withering’s work “was the turning point in the development of modern pharmacology and in its splitting away from traditional herbal medicine”. Herbal practitioners are no longer permitted to use foxglove, though they have an alternative in Lily of the Valley (Convallaria majalis) which contains similar cardiac glycosides but is less toxic.

      Caroline Wheeler:

Sources
Griggs, B. (1981). Green Pharmacy. Healing Arts Press.
Mabey, R. (1996). Flora Britannica. Sinclair-Stevenson.