Dishing the dirt on childhood infection
16 December 2009
Exposure to infections before birth and as a baby may reduce the risk of chronic diseases in later life, according to a recent study.
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Dr Annabel Bentley, assistant medical director, Bupa |
We need more research before we can conclude that dirt is good. 
Scientists looked at data from children born in the Philippines to see whether being exposed to more infections as an infant reduced levels of C-reactive protein (CRP) as a young adult. CRP is a protein in the blood that increases when there is inflammation in the body - a key part of the immune system response. Raised levels of the protein are known to be associated with conditions such as heart disease and diabetes.
Although it's known that inflammation plays an important role in immunity, it's not known how this develops. A theory called the 'hygiene hypothesis' argues that reduced exposure to infection as a young child increases your likelihood of developing allergies and hay fever - conditions that are associated with the immune system not working properly. This idea suggests that being exposed to infections is important in helping the immune system to develop correctly.
The researchers studied nearly 1,500 children over 18 years, beginning while they were still in the womb. They looked at how much infection they were exposed to, for example how many people lived in their household, the cleanliness of their living conditions and their source of drinking water. The researchers found that people who grew up to have raised levels of CRP were exposed to lower levels of animal faeces and had fewer bouts of diarrhoea as children. They also saw that children who had lower birth weights were more likely to have higher levels of CRP as young adults.
The authors of the study believe that being exposed to more infectious substances before birth and as a young child helps to develop the immune system. This exposure also seems to result in less inflammation indicating that chronic conditions such as heart disease aren't as likely.
Bupa's assistant medical director, Dr Annabel Bentley, said: "These findings are interesting but should be treated with care as they don't prove a causal link. We need more research before we can conclude that dirt is good - children should be raised in a safe, hygienic environment."
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Related information
Read the study
McDade TW, Rutherford J, Adair L, et al. Early origins of inflammation: microbial exposures in infancy predict lower levels of C-reactive protein in adulthood. Proc R Soc B 2009; doi:10.1098/rspb.2009.1795
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