You can either think natural remedies work - that they have powerful medicinal properties, can be used to treat infection or support the immune system etc and therefore also have side effects and you need to be careful with dosage
OR you can believe that they're totally safe, have no side effects, don't require precise dosage and therefore are basically inert. You can't have it both ways.
I don't dispute that natural remedies can have medicinal properties, but I want to see solid, double-blind, rigorously controlled trials that support their use. Resources like the Cochrane Library (for human medicine) are invaluable for bringing together evidence and giving access to meta-analyses - basically taking lots of studies conducted on a drug under similar conditions and collating them to identify trends in larger populations.
https://www.cochranelibrary.com/
You can read their analysis of research into echinacea as a preventative for the common cold here:
https://www.cochranelibrary.com/cds...ub3/full?highlightAbstract=echinacea|echinace
As
@Ripshod says, natural remedies are often variable in strength and potency - the reason we take aspirin tablets rather than chew willow bark is because the active ingredient has been isolated and we can control the dosage precisely. We don't have to guess the potency based on growing season, weather etc. There are no standard formulations for echinacea: the preparations we can buy are often manufactured in different ways, available in different forms, use material from different species, use different parts of the plant (roots, flowers, juice etc) that are grown and harvested in different conditions, and are made to different strengths.
I don't mind experimenting on myself, but I refuse to subject Leia to substances that could be difficult for her digestive system, kidneys and liver to process without having a measurable benefit.