Avidin is a glycoprotein extracted from egg white using ion-exchange or affinity chromatography. Its biological importance was discovered in 1926 when rats were fed egg white and developed dermatitis, loss of hair and disruption of muscular co-ordination. It was determined that avidin has an extremely strong binding for biotin (Vitamin H), an important growth factor, which is three to six orders of magnitude higher than that of typical antigen-antibody complexes. When a large quantity of avidin was added to the diet of rats, it effectively deprived them of this essential growth factor. Biotin is found in every living cell, but most notably in kidneys, livers, and pancreas, as well as in yeast and milk.

Further research established that one avidin molecule can combine with four biotin molecules. Once biotin was synthesized in 1941, the use of avidin-biotin technology as a research tool became practical and effective for a variety of applications and technologies.