I have never heard of the term "astringent" used with bar oil. Doesn't seem to make sense, Hence the definition:
astringent, any of a group of substances that cause the contraction or shrinkage of tissues and that dry up secretions. Astringents are usually classified into three groups according to their mode of action: (1) those that decrease the blood supply by narrowing the small blood vessels (e.g.,
epinephrine and
cocaine), (2) those that abstract
water from the tissue (e.g.,
glycerol and
alcohol), and (3) those that coagulate the superficial tissue layers into a crust (e.g., metallic astringents, such as
calamine or
alum). Used in medicine to reduce swollen mucous membranes that result from inflammations of the nasal, gastrointestinal, and urinary passages, astringents are also frequently employed to dry up excessive secretions and (in this connection they are often known as styptics) to stop bleeding.