Sometimes we need to use synthetic ingredients to help with the formulation, we never use nasty ingredients, only safe ingredients for skincare. 
Ingredients affecting 100% Natural Claims and what they do:

Phenoxyethanol is a widely used synthetic preservative that has global approval for use in all cosmetic products in concentrations up to 1%. We stick to below this level. 

Caprylyl Glycol gives the skin a nice, soft feel as well as boosting the effectiveness of other preservatives, such as Phenoxyethanol.

Potassium Sorbate is a mild synthetic preservative that prevents Yeast and Mold.

Sodium Benzoate is a preservative used to prevent fungi.