In a complex ecosystem … DON’T POLLUTE.
Synthetic ingredients tend to pollute the ecosystem and compromise the microbiome. Synthetic ingredients such as fragrances, colourants and preservatives often leave a chemical residue on the skin, causing skin sensitivity, impaired skin barrier function and an overactive immune system, which can have knock-on effects on the microbiome.
The human symbiont is not well adapted to synthetics. There will almost always be unintended consequences when you add synthetic chemicals to a complex system.