Allergies represent an exaggerated response by the body’s immune system to substances that are typically harmless to most individuals, such as pollen, certain foods, or pet dander. These reactions can range from mild discomforts like sneezing or rashes to severe, life-threatening conditions.
Early Observations of Peculiar Reactions
Long before the scientific understanding of allergies emerged, ancient civilizations observed and documented unusual reactions to common substances. Around 3000 BC, the Egyptian pharaoh Menes may have died from a bee sting, an event now interpreted as a severe allergic reaction. These early accounts were observational, lacking any insight into the underlying biological processes.
The Greek physician Hippocrates, in the 5th century BC, described individuals who experienced adverse symptoms after consuming specific foods. He also noted connections between respiratory ailments, such as asthma-like symptoms, and environmental factors. Ancient Roman texts mention instances of peculiar sensitivities, like Emperor Claudius’s son Brittanicus developing a rash after contact with horses. The poet Lucretius captured this ancient understanding with the phrase, “food for most, poison for some,” acknowledging that certain substances affected individuals differently.
The Scientific Breakthroughs
A significant step toward understanding extreme bodily reactions occurred in the early 20th century with the work of French physiologists Charles Richet and Paul Portier. In 1901, while on a scientific expedition, they began studying the venom of the Portuguese man-of-war and sea anemones. Their initial goal was to determine if repeated, small doses of venom could induce immunity in animals.
Richet and Portier conducted experiments on dogs, injecting them with sublethal amounts of sea anemone toxin. Unexpectedly, they observed that a second, even smaller, dose of the same venom administered after an interval did not create protection but instead triggered a severe, rapid, and often fatal reaction.
To describe this unforeseen and intensified sensitivity, Richet coined the term “anaphylaxis,” derived from Greek words meaning “against protection.” This discovery profoundly changed the understanding of the immune system, revealing that it could not only protect but also cause extreme, harmful responses. For his groundbreaking work on anaphylaxis, Charles Richet was awarded the Nobel Prize in Physiology or Medicine in 1913.
Coining the Term “Allergy”
While anaphylaxis described a severe, harmful immune response, the broader concept of “allergy” was introduced in 1906 by Austrian pediatrician Clemens von Pirquet. He observed that patients who had previously received injections of substances like horse serum or smallpox vaccine, reacted differently to subsequent exposures. These reactions were often quicker and more pronounced than the initial response.
Von Pirquet recognized that the body’s reactivity to a foreign substance could be fundamentally altered by a prior encounter, leading to a “changed reaction.” He derived “allergy” from the Greek words “allos” (“other” or “different”) and “ergon” (“reaction” or “work”).
This new term described a broader phenomenon of “altered reactivity” by the immune system, distinguishing it from Richet’s specific focus on life-threatening anaphylaxis. Von Pirquet’s concept recognized that the immune system’s response to an antigen was not always protective, but could lead to various forms of hypersensitivity. His definition laid the foundation for understanding the wide spectrum of immune-mediated reactions, including those now commonly recognized as allergic conditions.