Allergies represent the immune system’s overreaction to substances typically harmless to most individuals. Reactions range from mild discomfort, like sneezing or skin rashes, to severe, life-threatening responses. Understanding this complex phenomenon involves tracing observations and scientific breakthroughs across centuries, marking a shift from anecdotal recognition to detailed scientific comprehension.
Early Clues and Ancient Observations
Long before the term “allergy” existed, ancient civilizations observed unusual sensitivities to various environmental factors and foods. One of the earliest reports dates back to ancient Egypt, with the legend of Pharaoh Menes, believed to have died from an anaphylactic shock after a wasp sting between 3640 and 3300 BCE. While direct evidence is scarce, this account suggests early awareness of severe reactions to certain triggers.
The Greek physician Hippocrates, often called the “Father of Medicine,” documented adverse reactions, linking respiratory problems in blacksmiths and stonemasons to their occupations. He described individuals who became ill after consuming specific foods, noting, “what is food for some may be fierce poisons for others.”
Roman philosophers, such as Lucretius, similarly observed disproportionate responses to common substances. These early observations, though lacking scientific explanation, demonstrated an awareness of individual sensitivities aligning with modern understandings of allergic reactions.
The Coining of “Allergy” and Early Theories
The systematic study and naming of these unusual reactions began in the late 19th and early 20th centuries. In 1902, French physiologist Charles Richet and Paul Portier made a groundbreaking discovery while researching immunity to sea anemone toxins. They observed that dogs, after an initial non-lethal exposure, reacted violently and sometimes fatally to a second, even smaller, dose. This unexpected “against protection” response led them to coin the term “anaphylaxis,” for which Richet received the Nobel Prize in 1913. Their work demonstrated that the immune system could produce harmful rather than protective effects.
A few years later, in 1906, Austrian pediatrician Clemens von Pirquet introduced the term “allergy.” Pirquet observed that some patients receiving diphtheria antitoxin developed quicker, more severe reactions to subsequent injections. He used the Greek words “allos” (other) and “ergon” (work) to create “allergy,” signifying an “altered reactivity.” Pirquet’s initial concept of allergy was broad, grouping conditions like asthma, hay fever, and eczema under this new umbrella term.
The Immune System’s Role in Allergic Reactions
A more profound understanding of the biological mechanisms of allergic reactions emerged in the mid-20th century. Scientists began identifying specific immune system components responsible for these responses. A significant breakthrough occurred in the late 1960s with the independent discovery of Immunoglobulin E (IgE).
In 1966-1967, a Japanese husband-and-wife team, Kimishige and Teruko Ishizaka, identified a unique class of antibody responsible for allergic reactions. Simultaneously, Hans Bennich and S. Gunnar O. Johansson characterized a new immunoglobulin that corresponded to the same antibody. These two groups collaboratively confirmed their findings, and the new antibody class was officially named IgE in 1968. The Ishizakas further demonstrated IgE’s role in triggering histamine release from mast cells, immune cells abundant in tissues. Histamine, a chemical mediator, is largely responsible for common symptoms of immediate hypersensitivity reactions, such as swelling, itching, and increased mucus production; this discovery of IgE provided a concrete explanation for immediate allergic responses, transforming understanding, diagnosis, and treatment.