[1] It works by neutralizing the toxins produced by Corynebacterium diphtheriae.

[4] The 1901 diphtheria antitoxin contamination incident, in which the milk wagon horse used to culture the antitoxin became infected with tetanus, which contaminated vials of the antitoxin leading to the deaths of several children in the midwest United States,[5] led to the passage of the Biologics Control Act of 1902 and the 1906 formation of the U.S. Food and Drug Administration (FDA).

[6][7] The celebrated 1925 serum run to Nome was a transport of the antitoxin by dog sled relay across the U.S. territory of Alaska across 674 miles (1,085 km) in 5+1⁄2 days, saving the small town of Nome and the surrounding communities from an epidemic of the disease.

Diphtheria antitoxin is on the World Health Organization's List of Essential Medicines.

[10] It is a solution of concentrated proteins, chiefly globulins, containing antibodies obtained from the blood of horses that have been immunized against diphtheria toxin.