TrialAnnals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology2008

Effects of echinacea on the frequency of upper respiratory tract symptoms: a randomized, double-blind, placebo-controlled trial.

Joelle O'Neil et al.PubMed ↗Full text ↗Publisher ↗

No numbers read from the abstract.