April showers bring May flowers—and seasonal allergies. For people who suffer from hay fever and other sensitivities—between 10 and 30 percent of the world’s population—pollen season can be an ordeal. But they can take some comfort in reflecting on the astounding progress that’s been made in treating these common—and potentially dangerous—maladies.
Allergies were known in ancient times, of course, and everyone from the Egyptians to the Romans had folk remedies for them. But only in the 19th century was pollen identified as the cause of hay fever. Also known as “allergic rhinitis” (from “rhinos,” Greek for “nose”), this condition is an inflammation of the nasal passages that, along with other symptoms, results when the immune system misidentifies pollen as a pathogen. In the 1900s, an Austrian pediatrician named Clemens von Pirquet coined the word “allergy” to describe the way patients often reacted severely to the second dose of a vaccine. Somehow the first dose, he realized, was priming their bodies to respond to the second.
The causal mechanism of allergies wasn’t understood until the 1950s, when scientists discovered that so-called mast cells work with white blood cells to fight what the body thinks are infections. When an allergen enters the bloodstream, a type of white blood cell called a B-lymphocyte produces a protein, immunoglobulin E, or “IgE,” tailored to that specific allergen. Like a targeting beacon, the IgE then signals mast cells to release chemicals that ordinarily help fight disease. The best known of these chemicals is histamine, which causes the itching and sneezing associated with seasonal allergies.
The first, and still most common anti-allergy medicines were designed to treat this unnecessary histamine release. Antihistamines such as diphenhydramine hydrochloride (Benadryl)—first sold in the United States in 1946—dampen histamine’s effects and relieve symptoms but have a well-known downside: They can cause drowsiness. . . .
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1. Leon Kass, “Preventing a Brave New World,” The New Republic Online, June 21, 2001, https://web.stanford.edu/~mvr2j/sfsu09/extra/Kass3.pdf (accessed May 20, 2019).