Like other members of Ranunculaceae family, blisterwort contains ranunculin, which turns into a bitter oily toxin called protoanemomin when the plant is injured. You may be tempted to touch the beautiful blooms of the blisterwort, but it may cause contact dermatitis in people with sensitive skin. Inhaling vapor or smoke from the burning plant can cause respiratory problems. Ingesting the plant is dangerous too, although symptoms only usually occur when larger quantities have been consumed. Symptoms include a burning sensation in the mouth, swelling in the tongue and excess saliva production. Fortunately, the extremely bitter taste of the blisterwort is enough to persuade people not to eat them. Considering that there are no clinical trials that support the remedial effects of blisterwort on ulcers and hemorrhoids, never use it as medicine, especially improperly prepared ones.