This article has been excerpted from Sniff: A History of Smells by William Tullett, new from Yale University Press. Copyright © 2026 William Tullett. Published by permission. All rights reserved.

Air, land, and sea. Our world is characterized by a proliferating variety of uncertain scents. Yet our noses are ill-equipped to discern between them. Pollution, pandemics, and poverty have conspired to reduce our sensitivity. Some gases, such as the rotten-egg stink of hydrogen sulfide emitted by industries and waste sites, induce a selective loss of smell. These substances are most dangerous when they are least odorous.

When we try to use our noses, the result can be confusion. Supermarkets across the globe have begun to remove “best before” dates from products such as milk and yogurt in an attempt to avoid food waste. They have encouraged consumers to deploy the sniff test to distinguish the sweet, mild, scent of fresh milk from a sour spoiled odor.…