Botanical drugs and supplements affecting the immune response in the time of COVID-19: Implications for research and clinical practice

Thomas Brendler, Ahmed Al-Harrasi, Rudolf Bauer, Stefan Gafner, Mary L. Hardy, Michael Heinrich, Hossein Hosseinzadeh, Angelo A. Izzo, Martin Michaelis, Marjan Nassiri-Asl, Alexander Panossian, Solomon P. Wasser, Elizabeth M. Williamson

Research output: Contribution to journalReview articlepeer-review


In times of health crisis, including the current COVID-19 pandemic, the potential benefit of botanical drugs and supplements emerges as a focus of attention, although controversial efficacy claims are rightly a concern. Phytotherapy has an established role in everyday self-care and health care, but, since botanical preparations contain many chemical constituents rather than single compounds, challenges arise in demonstrating efficacy and safety. However, there is ample traditional, empirical, and clinical evidence that botanicals can offer some protection and alleviation of disease symptoms as well as promoting general well-being. Newly emerging viral infections, specifically COVID-19, represent a unique challenge in their novelty and absence of established antiviral treatment or immunization. We discuss here the roles and limitations of phytotherapy in helping to prevent and address viral infections, especially regarding their effects on immune response. Botanicals with a documented immunomodulatory, immunostimulatory, and antiinflammatory effects include adaptogens, Boswellia spp., Curcuma longa, Echinacea spp., Glycyrrhiza spp., medicinal fungi, Pelargonium sidoides, salicylate-yielding herbs, and Sambucus spp. We further provide a clinical perspective on applications and safety of these herbs in prevention, onset, progression, and convalescence from respiratory viral infections.

Original languageEnglish
Pages (from-to)3013-3031
Number of pages19
JournalPhytotherapy Research
Issue number6
StatePublished - Jun 2021

Bibliographical note

Publisher Copyright:
© 2020 John Wiley & Sons, Ltd.


  • Boswellia
  • COVID-19
  • Curcuma
  • Echinacea
  • Glycyrrhiza
  • Pelargonium
  • Sambucus
  • adaptogens
  • herbal medicine
  • medicinal fungi
  • phytotherapy
  • salicylate

ASJC Scopus subject areas

  • Pharmacology


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