There are studies that will show the common allergic disease like hay fever, eczema and other food allergies that are found less often in children from larger families. These things will hold the immune system back with its development. This is because of the lack of dirt and germs that the immune system does not learn what it should in order to protect the body from. This is going to allow it to go after other things that are not going to be good for the body and it can cause a problem with an allergy in just about anyone. With children sometimes...