Mistletoe for Cancer

Mistletoe for Cancer: Safety & Side Effects

This page covers safety information for Mistletoe (European). See our complete Mistletoe for cancer therapy guide →

Author

Olivia Pearman, PhD

Research Associate

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Olivia Pearman is an experienced researcher who is passionate about access to scientific information. She has over a decade of research experience with a PhD from the University of Colorado at Boulder, a Master’s from the Yale School of the Environment, and a Bachelor of Science from Clemson University. Throughout her career, she has honed her skills in translating research for all audiences and is thrilled to work with CancerChoices to help make scientific knowledge available for everybody.

Olivia Pearman, PhD Research Associate

Clinical reviewer

Sarah Soles, MSc, ND, FABNO

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Dr. Sarah Soles completed her naturopathic medical training at the Canadian College of Naturopathic Medicine. During her internship on the adjunctive cancer care shift, she learned the immense value of combining naturopathic approaches with conventional cancer treatments. Dr. Soles went on to complete a two-year residency in naturopathic cancer care at the Integrated Health Clinic. She continues to help patients in all stages of their cancer journey—from screening and prevention to active treatment or maintaining a remission. She is also the research director for the Knowledge in Naturopathic Oncology Website and a contributing author to the Textbook of Naturopathic Oncology: A Desktop Guide to Integrative Cancer Care.

Sarah Soles, MSc, ND, FABNO

Last update: May 6, 2026

Is mistletoe safe?

Supervision by a medical professional is highly recommended because of potential for allergic reactions and interactions with other treatments, especially at higher doses.

Interactions with cancer treatment

In general, studies have not shown a negative impact on treatment outcomes when mistletoe extracts are combined with traditional cancer treatments such as radiation, chemotherapy, targeted therapies, or immune checkpoint inhibitors.¹Paller CJ, Wang L, et al. Phase I trial of intravenous mistletoe extract in advanced cancer. Cancer Research Communications, 2023;3(2):338-346; Schad F, Thronicke A. Safety of Combined Targeted and Helixor®Viscum album L. Therapy in Breast and Gynecological Cancer Patients, a Real-World Data Study. International Journal of Environmental Research and Public Health, 2023;20(3), 2565; Thronicke A, Steele M, et al. Clinical safety of combined therapy of immune checkpoint inhibitors and Viscum album L. therapy in patients with advanced or metastatic cancer. BMC Complementary and Alternative Medicine, 2017;17(1):534.

Side effects and adverse reactions

Mistletoe extracts are most commonly administered subcutaneously or intravenously, but there are also studies that have applied mistletoe directly into tumors or into the bladder or pleural space. Fever and redness or irritation at the injection site are the most common side effects for subcutaneous administration of mistletoe extracts and are generally mild.²Mistletoe (Viscum album). Centre for Health Innovation. February 2024. Viewed May 28, 2024; Pelzer F, Tröger W, Nat DR. Complementary Treatment with Mistletoe Extracts during Chemotherapy: Safety, Neutropenia, Fever, and Quality of Life Assessed in a Randomized Study. Journal of Alternative and Complementary Medicine. 2018;24(9-10):954-961; Horneber MA, Bueschel G, et al. Mistletoe therapy in oncology. Cochrane Database of Systematic Reviews, 2008;(2):CD003297. Other common side effects include:³Steele ML, Axtner J et al. Adverse drug reactions and expected effects to therapy with subcutaneous mistletoe extracts (Viscum album L.) in cancer patients. Evidence-Based Complementary and Alternative Medicine, 2014;2014:724258.

There are variations in side effects across administration methods.⁴Steele ML, Axtner J, et al. Safety of Intravenous Application of Mistletoe (Viscum album L.) Preparations in Oncology: An Observational Study. Evidence-based Complementary and Alternative Medicine : eCAM, 2014;236310; Steele ML, Axtner J, et al. Use and safety of intratumoral application of European mistletoe (Viscum album L) preparations in Oncology. Integrative Cancer Therapies, 2015;14(2), 140–148; Schad F, Atxner J, Buchwald D, et al. Intratumoral Mistletoe (Viscum album L) Therapy in Patients With Unresectable Pancreas Carcinoma: A Retrospective Analysis. Integrative Cancer Therapies. 2013;13(4):332-340; Rose A, El-Leithy T et al. Mistletoe Plant Extract in Patients with Nonmuscle Invasive Bladder Cancer: Results of a Phase Ib/IIa Single Group Dose Escalation Study. The Journal of urology, 194(4), 939–943; Chang Y, Cho D, Cho K, Cho M. Viscum pleurodesis is as effective as talc pleurodesis and tends to have less adverse effect. Supportive Care in Cancer. 2020;28(11):5463-5467

Serious adverse reactions are rare, but may occur.⁵Cogo E, Elsayed M, et al. Mistletoe Extracts during the Oncological Perioperative Period: A Systematic Review and Meta-Analysis of Human Randomized Controlled Trials. Current Oncology (Toronto, Ont.), 2023; 30(9), 8196–8219; Huber R, Schlodder D, et al. Safety of intravenously applied mistletoe extract—results from a phase I dose escalation study in patients with advanced cancer. BMC Complementary and Alternative Medicine. 2017 Sep 18;17(1):465; Schläppi M, Ewald C, et al. Fever Therapy With Intravenously Applied Mistletoe Extracts for Cancer Patients: A Retrospective Study. Integrative Cancer Therapies, 2017;16(4), 479–484; Augustin M, Bock PR, et al. Safety and efficacy of the long-term adjuvant treatment of primary intermediate- to high-risk malignant melanoma (UICC/AJCC stage II and III) with a standardized fermented European mistletoe (Viscum album L.) extract. Results from a multicenter, comparative, epidemiological cohort study in Germany and Switzerland. Arzneimittelforschung, 2005;55(1):38-49. Serious reactions include:⁶Mistletoe (Viscum album). Centre for Health Innovation. February 2014. Viewed May 28, 2024.

• Severe, potentially life-threatening allergic or pseudo-allergic reactions (anaphylaxis)⁷Casetti F, Rafei-Shamsabadi D, & Müller S. Grade II-anaphylaxis after subcutaneous injection of mistletoe extract. Contact Dermatitis, 2021;85(4), 462–465; Hutt N, Kopferschmitt-Kubler M et al. Anaphylactic reactions after therapeutic injection of mistletoe (Viscum album L.). Allergologia et Immunopathologia (Madr), 2001;29(5):201-3; Kienle GS, Grugel R, Kiene H. Safety of higher dosages of Viscum album L. in animals and humans–systematic review of immune changes and safety parameters. BMC Complementary and Alternative Medicine. 2011 Aug 28;11:72; Bauer C, Oppel T, Ruëff F, Przybilla B. Anaphylaxis to viscotoxins of mistletoe (Viscum album) extracts. Annals of Allergy, Asthma and Immunology. 2005;94(1):86-89.
  • Swelling of throat, skin and mucous membranes (angioedema)
  • Low blood pressure (hypotension) 
  • Loss of consciousness
• Skin infection (cellulitis) at the injection site
• Increased intracranial pressure (in cases of brain tumors or brain metastases) 
• Increased liver enzymes (with intravenous mistletoe application)⁸Paller C, Wang L, Fu W et al. Phase I Trial of Intravenous Mistletoe Extract in Advanced Cancer. Cancer Research Communications. 2023;3(2):338-346; Lederer AK, Rieger S, Schink M, Huber R. Pharmakokinetics of Mistletoe Lectins after Intravenous Application of a Mistletoe Product in Healthy Subjects. Pharmaceuticals (Basel, Switzerland). 2024 Feb 22;17(3):278.

Contraindications

Potential contraindications are existing fever or infection, pregnancy, hyperthyroidism, and organ failure.The safety for use with autoimmune conditions or under immunosuppressive therapy is unclear, but given their immunostimulatory action, it is best to discuss with your doctor. Caution and close supervision is required when using mistletoe in those with primary brain cancer, spinal cord tumors, or brain metastases due to the risk of increased intracranial pressure.⁹McKinney N. Naturopathic Oncology, 3rd Edition. Victoria, BC, Canada: Liaison Press. 2016; Oei SL, Thronicke A, et al. Use and Safety of Viscum album L Applications in Cancer Patients With Preexisting Autoimmune Diseases: Findings From the Network Oncology Study. Integrative Cancer Therapies, 2019;18, 1534735419832367.

Drug interactions 

There are potential interactions with drugs like immunosuppressants and anticoagulants. Mistletoe should only be used with the supervision of a healthcare professional. 

Potential drug interactions: 

• Immunosuppressants¹⁰EfficaSafe. 2026. Accessed Jan 28, 2026.
• Anticoagulants¹¹Moussouni M, Graff V, et al. Drug Interactions Causing Warfarin Overdose in a Patient with Pancreatic Cancer: A Case Report. Chemotherapy. 2023;68(2), 111–114; EfficaSafe. 2026. Accessed Jan 28, 2026. 
• Caution with antiplatelets and antihypertensives

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