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.

Isopropyl Alcohol has been used to help mix Behentrimonium Chloride (a great conditioning ingredient naturally derived from Colza Oil) and is found at a very low level in the finished conditioner (less than 0.5%).