Exposure to bacteria is the best form of immunisation.
|Befriend thy bacteria
|Until recently, it had been thought that the rise in cases of these diseases in the West was linked to vaccines, drugs and better hygiene, which meant children's immune systems were not being tested as rigorously as they should be.
|However, it is now thought that a lack of exposure to harmless bacteria, which can be found in mud, rotting vegetables and on animals and tiny worms, is actually the problem.
|Without enough of "switch off" cells - ones that recognise the friendly bacteria - to regulate the immune system, it can go into attack mode too easily and decide that an "invading enemy" like pollen must be destroyed.
|Graham Rook, professor of Immunology at the University College Medical School, London, says "mud bugs" and others could hold the key to effective treatment of a whole range of allergies.
|"It is believed these organisms have been present throughout our evolutionary history. And because the immune system would be expecting to see them throughout evolutionary history, when it does see them it says, 'ah, old friends' and turns off the immune response. Most of the time the immune response has to switch itself off - it mustn't attack your breakfast, your lunch, not to mention all the stuff you are breathing in all day. Its main job is not attacking."
|The immune system has two main kinds of cells - dendritic cells, which establish whether something is dangerous or not, and lymphocytes, which attack any threat."If you don't have the harmless bacteria, you don't have enough dendritic cells," Rook says.
|The new thinking is starting to be used by scientists across the world to produce new treatments for allergies. Rook's team has developed a vaccine to treat eczema and asthma, which has shown encouraging results. A study by scientists at Iowa University in the US found that giving 2,500 pig worm eggs once every three weeks to people with Crohn's disease, a bowel condition, resulted in the disappearance of symptoms in 21 of 29 cases. -