It is also claimed that bone metastases are retarded in some cases. Results appear less promising for inoperable cancers of the breast, lungs and esophagus. It is thought that tumor growth slows or stops, and then gradual regression begins. It is believed that tumor cells are transformed first to a semi-malignant form, then to chronic inflammation and finally to normal tissue. Mistletoe contains a cytotoxic lectin, viscumin.
Various lectins are both cytotoxic and immunostimulatory.
It usually produces an increase in body temperature and flu-like symptoms. In addition, the injection site can become inflamed and abdominal pain with nausea may occur. Overdoses, however, can cause severe poisoning including seizures, coma and death. Even a few leaves or berries can cause poisoning, so never eat part of a mistletoe plant and keep the plants away from animals and children. The combination can cause dangerously high blood pressure.