Scientists are slowly coming round to an idea which grandmothers have instinctively known for decades childhood illnesses help 'train' the immune system.
The latest theory is that childhood infections such as measles, mumps and rubella, as well as early exposure to other infective organisms such as Toxoplasma gondii, Helicobacter pylori and the hepatitis A virus can lower the risk of developing atopic disease and respiratory allergies.
Italian scientists carried out a retrospective case control study comparing 240 men with atopy and 240 men without. They found that those not exposed to childhood infections were nearly three times more likely to have atopy than those who had been exposed to such pathogens.
The researchers also found that greater exposure to microbes transmitted from faeces through food reduced the likelihood of experiencing atopy.
The study concluded that exposure to pathogens may stimulate the gut associated lymphoid tissue necessary to prevent atopy and allergies (BMJ, 2000; 320: 412-7)