DOES IT WORK?
BACKGROUND
Benzoin is a term used with a number of traditional remedies. The products are made from a resin obtained from a group of Styrax trees which grow in warm and tropical regions. The resin is produced after a wound is cut into the bark of trees that are at least seven years old. The resin hardens to give a grey-brown solid with a vanilla-like odour. Up to one-third of the resin is benzoic acid, which is a food preservative and has mild anti-microbial properties. The resin comes in different forms and qualities depending on where it is harvested, leading to names like Siam Benzoin and Sumatra Benzoin. The resin is primarily used to make incense, perfume and medicinal tinctures.
Tincture of benzoin is made by soaking benzoin resin in alcohol. The purest resins will dissolve completely, but lesser grades require filtering. What remains is usually a 10 per cent solution of benzoin resin. The tincture is most commonly used by applying it to the skin and then attaching a bandage. This is done as a mild antiseptic, to protect sensitive skin that might have an allergic reaction to bandage adhesives, and to help the bandage adhere longer. The tincture is also poured into boiling water as an inhalant to relieve congestion from colds and bronchitis.
Compound benzoin tincture is an officially recognised mixture of benzoin resin, aloe, tolu balsam and storax, dissolved in alcohol. The latter two products are resins derived from other trees. Friar’s Balsam is based on compound benzoin tincture but contains additional resins. All the tinctures are traditionally used either topically as an antiseptic and adhesive for bandages, or as an inhalant for respiratory problems.
Benzoin oil is an extract of the resin made using organic solvents which are then evaporated. What remains is the water insoluble fraction of the resin. This oil is used to clear chest congestion, but is also said to clear the mind and relieve anxiety. Benzoin resin or tincture should not be confused with benzoin used in the polymer industry. This white crystalline chemical is unrelated to the plant material and does not have any medicinal uses.
EVIDENCE FROM STUDIES
In spite of being used for more than a century, very little systematic study of benzoin’s effectiveness has been carried out for any indication. A small study found that benzoin products did not lead to fewer allergic reactions with bandages than other barriers. Another small study found that relief from congestion was similar using steam from boiling water alone compared to boiling water with benzoin tincture.
PROBLEMATIC ASPECTS
Tincture of benzoin is sometimes used in conventional medical settings and can lead to allergic reactions. Such allergic reactions occur more commonly in people prone to contact dermatitis, who ironically may be using benzoin to prevent allergies to bandages. Other barrier sprays are now available which are less allergenic. A study in Australia found that almost 10 per cent of patients were allergic to compound benzoin tincture. One- third of these were rated as “strong reactions”, almost all of which occurred in people with allergies to other natural oils and resins. A small number of cases of poisonings have been reported when people mistakenly drank benzoin tinctures intended for use as inhalants. Severe stomach irritation occurred leading to bleeding into the stomach and stools. Patients recovered completely after several days.
RECOMMENDATIONS
Although various benzoin products remain popular, little or no controlled studies support their use. The few available studies found they were no more effective than other approaches that did not include plant resins. Given the relatively common incidence of allergic reactions to benzoin tinctures, other products would be preferable.
Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University.
