Dipropylene Glycol - DPG is not only a humectant (as it attracts and absorbs water) but is also a carrier for cosmetic ingredients in fragrances and cosmetics due to its lack of aroma to interfere with the intended scent profile.  It is effective when used as a solvent and coupling agent and can aid stability when freeze/thaw testing is used.

INCI: Dipropylene glycol
CAS# 25265-71-8

Usage Rate: 1-20% recommended in cosmetic applications

Dipropylene glycol can also be used to make a reed diffuser base for your home.  Given that different fragrance oils are made with different components this recipe can be tweaked and adjusted to suit the scents you are using
Dipropylene glycol - 20-60%
Fractionated coconut oil - 20-60%
Fragrance - 10-60%
Perfumers alcohol - 10-30%