Though some species of milkweed are very toxic (Spider milkweed or whorled milkweed), others were used for medical purposes. Butterfly-weed or Pleurisy-root (Asclepias tuberosa) was, and still is used today, in teas to treat lung ailments. The sap of showy milkweed was used to treat skin ailments, such as warts, ringworms and poison ivy.