I am making a salt oil mix product. The essential oil smell is totally fading after 2 wks. Why is that?

I am useing salts, 5 different base oil, citrus, spearmint %26amp; peppermint essential oils %26amp; vitamin e

I am making a salt oil mix product. The essential oil smell is totally fading after 2 wks. Why is that?
You need to add arrow root pwwder in order to keep the essential oils from evaporating so fast. It is their nature to do that, only some organic substances like sugar or some starches (sorry not sure about any other but arrow root) somehow bind the smell and keep it for months.