The “hygiene hypothesis” for allergic disease is a misnomer

A publication by David Strachan in The BMJ in 1989 described the idea that a loss of species diversity from the ecosystem of the human body could lead to allergic disease.1 Subsequent studies have focused on exactly which species of symbionts might be important,2 and they have expanded the model beyond allergy to include autoimmune diseases3 and cognitive disorders related to inflammation.4 This view, now confirmed by a vast body of literature as a cornerstone of immunology, is likely to affect the discipline of cancer study in the future.5

Strachan’s view can be accurately described as “biome depletion,” an evolutionary mismatch that works in tandem with other mismatches (for example, inflammatory diets and vitamin D deficiency) to undermine immune function in industrialized societies.6 Strachan articulated his quantum leap of thinking in his 1989 paper, stating, “These observations do …