Why do people think all natural is safer?

Both my mother and girlfriend are like this. I never understood it. "It's from nature, it's not "chemicals" ". When I try to explain chemicals are natural as well, they say "No, chemicals are man made". Sadly, this seems to be a very popular belief, not just with my mother and girlfriend. Chemicals occur in everything, natural or man made. Natural doesn't mean safer. I don't know if people with this mindset think anything that is man made is equivalant to fucking anti-freeze or something, or what. Natural can be just as dangerous if not more. Biggest example is medication. People think self medicating with herbs and plants is safer. You're not a doctor, you have no idea what dose to take, and everything you need to know. Googling it doesn't mean you know everything you need to know.
Why do people think all natural is safer?
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