If there's anything that doesn't contain "mystery ingredients" it's going to be pharmaceuticals. Very few things are as controlled and monitored as the formulation and production of medicine.

The average layperson can't understand what all the ingredients are or what they do but that is a consequence of having a society with specialisation of work and it's no more alarming than the average layperson not knowing how apple trees are pruned. Something doesn't become a mystery simply because understanding it takes some effort.