The Brucellin Skin Test (BST) is a cell-mediated immune assay which is based on the use of purified and standardised protein allergen, almost completely devoid of lipopolysaccharide. The BST relies on the delayed-type hypersensitivity reaction whose results are interpreted 48 and 72 hours post brucellin injection in small Ruminants and Cattle respectively.

Therefore an animal is restrained twice: to administer brucellin, and to read the result.