Lars Klintwall Malmqvist ( Larsklintwallmalmqvist ) ? Public domain
Quick facts
David Strachan noted less hay fever in larger families and coined the hygiene hypothesis in the BMJ.Strachan 1989
Graham Rook argued we need microbes we co-evolved with — not street dirt or a skipped vaccine.Old Friends 2003
Chlorination and sewage cut cholera and typhoid. That success is not cancelled by allergy trends.Clean water saves lives
European farm-child studies linked livestock exposure and raw-milk contexts to lower atopy — correlation with caveats.ALEX farm studies
As worms and some infections fell in rich countries, some immune-mediated diseases rose — a pattern, not a prescription to seek worms.Helminth decline
The useful claim is missing old partners and diversity, not that open sewers or unwashed hands are medicine.Not dirt-is-healthy
The hygiene hypothesis began as an observation about family size and hay fever, not as a slogan that dirt is medicine.
Clean water, sewers and vaccines saved more lives than any romantic idea of a muddy childhood. Balance means keeping those wins while asking why some immune diseases rose.
Old Friends thinking points to missing partners, not to drinking ditch water or skipping immunization.
The profile
Familiarity70
Medical weight50
Benefit60
Risk35
Research58
Live debate65
Risk
Clean water saves lives; missing old microbial partners is a separate, still-debated immune story.
