The most innocuous substances are somehow verboten. Paracetamol: fine. Canestan: only the weak version. Vicks: fine. Arnica: probably OK as a homeopathic pill but god forbid you apply the cream.
Anything which hasn’t had a double blind study of some type is dubious and therefore forbidden. Then there are various crunchy granola types who cast doubt on everything normal but chemical.
Googling to find all this out is time consuming. However, generally speaking, someone has asked the same question on a forum somewhere and there’s always someone reassuring about it.