Homeopathic Arnica can work well after trauma and surgery.
I'm afraid I don't know about what would be supportive during Chemo. I know that Echinacea and Astragulus are good herbs for immune support, but I do not know if they are safe for cats. I know for sure Echinacea is safe for dogs if used correctly. Not sure about Astragulus. However Echinacea shouldn't be used (for people or animals) if there is any auto-immune disease, or if there is any antibiotic treatment going on.
Chemo...? I don't know.
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