I've read that if you're allergic to ragweed, don't take echinacea. I'm allergic to ragweed and cannot eat certain fruits and vegetables that are related/cross-pollenated (watermelon, cucumbers, bananas, etc.). Allergies are weird that way.
There are supposedly other things, elderberry and the like. My local health food store has a combination liquid.
Early on, wasn’t echinacea listed as a do not take in CV times?