Dressing oil is a specially prepared oil applied to spell and ritual objects before using them to sanctify, charge and prepare them for use or after assembling them to charge and activate them. This is called “dressing” or “fixing” the object.
Dressing oils are often used to dress candles prior to burning them by completely coating the candle in the oil, or they may be used to dress and activate a mojo bag. Dressing oils may also be used to render mundane objects magical, for example, you may dress your money before betting it or investing it, to encourage it to come back to you.
Dressing oils are conjure oils, from Conjure or Hoodoo practice and many pre-made dressing oils can be purchased in Hoodoo and Voodoo establishments. The formulas for these oils are, in many cases, quite ancient in origin, combining African folk magic and medicine, with Native American folk magick and medicine, European written sources and what would have been available to regional practitioners.
Dressing oils are generally used for inanimate objects, while anointing oils are used for people. Thus, anointing oils must be safe to use on the skin, while dressing oils do not. However, there is no reason you can’t use a skin-safe dressing oil as an anointing oil or an anointing oil as a dressing oil.
I am combining a more general look at both these oils under conjure oils.
See also: conjure oil, anointing oil, condition oil, formula oil, perfume oil