Surprisingly, and contrary to popular opinion Mistletoe (Viscum album) is not specifically poisonous, however caution should probably be shown when trying it for the first time. Most plants with significant properties are also poisonous if not used properly. Mistletoe is a hemiparasite shrub, it has chlorophyll so is able to photosynthesise but take minerals, nutrients, and water from its host, usually broad-leaved trees such as apples, lime, poplar and oak trees. Ancient cultures, especially Druids have used it in fertility rites and in healing diseases such as tumours as well as insomnia and mental problems. However very sick people, pregnant and nursing mothers should never take mistletoe. Mistletoe may cause allergies in some people, so first-time users should be watchful for symptoms (swelling, difficulty of breathing, rashes, etc.) People who are taking drugs for medical conditions should consult their doctors first before taking mistletoe tea because of danger of drug interactions. For example, a person on anti-hypertensive medication who took mistletoe tea may experience dangerous drop of blood pressure. I prepare the Mistletoe Tea, using a teaspoon, large pinch, per person, boiling water for between five and ten minutes, an unusual, but not totally unpleasant taste, which I quite enjoyed.
It goes without saying that if you're pregnant (or are under the doctor for anything) caution should be exercised with herbal decoctions.