Clemens Peter Freiherr (Baron) von Pirquet (May 121874–February 281929) was an Austrian scientist and pediatrician best known for his contributions to the fields of bacteriology and immunology.

Born in Vienna, he studied theology at the University of Innsbruck and philosophy and the University of Leuven before he enrolled at the University of Graz where he became a doctor of medicine in 1900.

In 1906 he noticed that patients who had previously received injections of horse serum or smallpox vaccine had quicker, more severe reactions to a second injection. He, along with Bela Schick , coined the word allergy (from the Greek allos meaning "other" and ergon meaning "reaction") to describe this hypersensitivity reaction.

Soon after, the observation with smallpox led Pirquet to realize that tuberculin, which Robert Koch isolated from the bacteria that cause tuberculosis in 1890, might lead to a similar type of reaction. Mantoux expanded upon Pirquet's ideas and the Mantoux test, in which tuberculin is injected under the skin, became a diagnostic test for tuberculosis in 1907.

References

• Who Named It - Pirquet