Nov 12, 2012: What is the history behind the development of BAL?

The story behind British Anti-Lewisite (BAL) goes back to the time of World War I when there was the development of lewisite as a chemical warfare agent. Lewisite is a topical arsenical that comes as an oily, colorless liquid that has the odor of geraniums; however, it can be a vapor form as well.  Lewisite is classified as a vesicant or blistering agent. Vesicant agents cause tissue damage when combined with protein sulfhydryl groups. One attribute of Lewisite that distinguishes it from sulfur mustard (another vesicant) is the onset of the pain occurs shortly after contact with the Lewisite. Sulfur mustard has a latency period of hours after contact before the blistering occurs.

The British discovered dithiol 2,3 dimercaptopropanol which combines with lewisite to form a stable ring, thus reducing the toxicity of the lewisite. Thus the name became British Anti-Lewisite, although today it is also known as dimercaprol. For the topical vesicant exposures, the BAL was applied topically as part of the decontamination process. Topical BAL is no longer available.

Today, BAL is used for severe lead poisoning, arsenic, and inorganic mercury poisoning. It has a narrow therapeutic ratio and must be given intramuscularly. It is an oily liquid that is made of peanut oil so patients with a peanut allergy cannot receive this medication. It also cannot be administered to patients with G6PD deficiency. Adverse effects are common with its administration and include fever, burning sensation of mucus membranes, nausea, vomiting, muscle aches, sterile abscesses.


This question prepared by: Saralyn Williams, MD  Medical Toxicologist


I am interested in any questions you would like answered in the Question of the Week.  Please email me with any suggestion at


Donna Seger, MD

Medical Director

Tennessee Poison Center

Poison Help Hotline: 1-800-222-1222