Ditch the hygiene for a healthy heart

Affluent, modern babies live in a sanitized world. This has already been blamed for a high incidence of asthma and allergies, but might also up the risk of developing a host of other conditions common in rich countries, such as stroke and heart disease. According to the "hygiene hypothesis," the immune system evolved to handle a germ-laden world. If people don't encounter many pathogens during infancy, it doesn't learn to keep itself in check, and turns on inflammation--normally a response to infection--in inappropriate situations. This reaction, the hypothesis goes, is responsible for the recent increase in asthma and allergies, both associated with inflammation.