As many as one in five Americans may have allergies.
According to the UCLA Food & Drug Allergy Care Center, the hygiene hypothesis explains why so many people today have allergies. This hypothesis is that the excessive cleanliness of people today has interrupted the normal development of the immune system. This theory is that the human body needs to be exposed to germs and that some types of infection are part of the natural development of the human immune system. Today's good sanitation and lack of parasite infections is likely the cause of the epidemic of allergies.
Environment May Be Too Sterile
Children of today may be an only child who does not acquire infections from siblings, whereas years ago almost all children had siblings. Living on farms is no longer common since children typically live in sterile environments in cities or suburbs. When children lived on farms, they were exposed to a variety of germs and infections and they seldom took antibiotics. Many urban children of today have taken many doses of antibiotics that may have affected their immune system in some ways. The hygiene hypothesis contends that this change in lifestyle is likely responsible for the rise in allergies today.
Food Allergy Rates Increasing
The hygiene hypothesis also explains why food allergy, such as peanut allergy, rates are growing. Many doctors and allergists have suggested that parents with a family history of peanut allergy should delay introducing peanut butter and other peanut products to their children. The LEAP study in the UK showed that countries that introduce peanuts and other foods that have a high potential for producing an allergic reaction early in life have fewer food allergies. In countries that delay introducing peanuts, such as the U.S. where pediatric allergists recommend delaying solids until 4 to 6 months of age, there are higher rates of food allergies. Some doctors recommend that high risk foods like peanuts should not be introduced until a child is 3 or 4 years old.
Certain Foods Now Processed Differently
Today, peanuts are usually roasted, whereas they were once commonly boiled. This could be another reason why more children develop a peanut allergy reaction when they eat peanuts. Even those with egg allergy or milk allergy can sometimes tolerate these foods when they are baked. This shows that the form and preparation of the food makes a difference when considering if certain foods are safe to eat for people with food allergies.