Aconitum, also commonly known as aconite, monkshood, and wolfsbane, is a flowering plant. For ages, folklore has told of wolfsbane as having connections to werewolves, especially being able to harm them or keep them away. All good tales have basis in reality, and the same holds true for wolfsbane.
There are many varieties of Aconitum growing across the northern hemisphere, often in mountainous regions with wet but drained soil. They usually coincide with locations of wolves, in a coincidence that has not had any research done to test a connection. All varieties of Aconitum are poisonous, containing high levels of highly toxic alkaloid compounds. Werewolves seem to have developed some sort of particularly high sensitivity to these compounds.
The compounds in Aconitum, generically called aconitine, act as nerve agents, paralyzing and causing numbness across the body. Warm-blooded victims die of asphyxiation first, because their respiration abilities shut down before their heart stops beating.
Most victims are poisoned due to accidental ingestion, or absorbing aconitine through the skin when picking or rubbing against the leaves of the plant. Aconitine is easily absorbed through the skin.
In the case of werewolves, however, even inhalation of a pollen amount approximate to two flowers can cause breathing problems and mild cardiac symptoms for up to four hours. In humans, it takes the oozing sap of approximately eleven picked leaves to cause life-threatening symptoms; in werewolves, it takes two.
Marked symptoms may appear almost immediately, usually not later than one hour, and "with large doses death is almost instantaneous." Death usually occurs within 2 to 6 hours in fatal poisoning (20 to 40 mL of tincture may prove fatal). The initial signs are gastrointestinal including nausea, vomiting, and diarrhea. There is followed by a sensation of burning, tingling, and numbness in the mouth and face, and of burning in the abdomen. In severe poisonings pronounced motor weakness occurs and cutaneous sensations of tingling and numbness spread to the limbs. Cardiovascular features include hypotension, bradycardia, sinus tachycardia, and ventricular arrhythmias. Other features may include sweating, dizziness, difficulty in breathing, headache, and confusion. The main causes of death are ventricular arrhythmias and asystole, paralysis of the heart or of the respiratory center. The only post-mortem signs are those of asphyxia.
In the event of poisoning by contact, tingling will start at the point of absorption and extend up the arm to the shoulder, after which the heart will start to be affected. The tingling will be followed by unpleasant numbness.
Most werewolves have learned to avoid aconite, taking the tell-tale tingling and following numbness of their nasal passages as a warning of when they have entered a patch of wolfsbane.