Getting children to eat dirt or move to an animal farm is the 'theoretical recommendation' of a Swiss study examining the causes of allergies and asthma.
Over 800 children living in the countryside were tested for their susceptibility to asthma and hayfever. Some of the children lived on farms, thus exposing them to high levels of dust contamination - including particles of animal manure. Samples of dust were taken from the beds of both the farm and non-farm children, and correlated with their allergic sensitivity.
On the face of it, the findings defy common sense because the least allergic children were discovered to be the ones who slept in the dust-covered farm beds.
The explanation put forward by the researchers is that endotoxins (bacterial poisons) in the farm dust act as 'potent immunostimulants' and strengthened the child's immune system.
This ties in neatly with other studies showing that children growing up in pet-loving households have less asthma and allergies.
Timing appears to be crucial, however. The earlier the exposure to the endotoxins, the better - including even the first days of life.
In the past, the idea that eating a peck of dirt will bolster a child's health has been regarded as something of an old-wives' tale. But it has now been granted official status as the 'hygiene hypothesis' (N Engl J Med, 2002; 347: 869-77).