All parts of the plant contain various diterpenoid alkaloids, typified by methyllycaconitine, so are very poisonous. In small amounts, extracts of the plant have been used in herbal medicine. Gerard's Herbal reported that drinking the seed of larkspur was thought to help against the stings of scorpions, and that other poisonous animals could not move when covered by the herb, but that he did not believe this himself. Grieve's herbal reports that the seeds can be used against parasites, especially lice and their nits in the hair. A tincture is used against asthma and dropsy. The juice of the flowers, mixed with alum, gives a blue ink. The plant was connected to Saint Odile, and in popular medicine was used against eye diseases