Tincture of benzoin is a pungent solution of benzoin resin in alcohol. A similar preparation called Friar's Balsam or Compound Benzoin Tincture (USP) contains, in addition, Cape aloes and storax (liquidambar resin). The latter was invented by Dr Joshua Ward around 1760.
Tincture of benzoin has two main medical uses: as a treatment for damaged skin in the "Compound" form, and as an inhalant in the non-Compound form.
Compound Tincture of Benzoin (CTB) is often applied to skin before applying tape or other adhesive bandages. To some degree, it protects the skin from allergy to the adhesive in the tape or bandage, but mostly it makes the tape or bandages adhere much longer. It is also used by athletes for its reputation of toughening skin exposed to the tincture. Orthopedists applying a cast often spray CTB in an aerosol can onto skin before casting, as it protects the skin under the cast, and diminishes itching.
It can be applied to minor cuts as a styptic and antiseptic (an effect of both the benzoin and its alcohol solvent).
As plain Tincture of Benzoin, it is also used as an oral mucosal protectant, for recurring canker sores, fever blisters, and the like.
Plain Tincture of Benzoin can also be inhaled in steam as a treatment for various conditions including bronchitis and colds. There is some disagreement as to whether or not benzoin should be used as a treatment for asthma.
It is used in the U.S. military to treat blisters. A common treatment utilized by medics in the U.S. Army is to drain the fluid from a blister and then inject enough compound tincture of benzoin into the void to glue the blister to the underlying skin, to serve as a local antiseptic, and to prevent further abrasion or loss of skin. This is commonly known as a "hot shot" amongst military personnel due to the extreme burning sensation that will be experienced for several moments when the tincture is applied.