Between 1 and 2 percent of adults have food allergies. Costs All told, allergies rank sixth in cost on the list of chronic diseases in the United States. Children lose about 2 million school days. How Allergies Develop How people become allergic is still something of a mystery. Because this period of sensitization varies so much, one person can develop a contact allergy during infancy while another may not be sensitized until adulthood.
Some children can outgrow one allergy only to develop another later in life.
If you have allergies, chances are you're carrying on a family tradition. A child with one allergic parent has a 30 to 50 percent chance of developing allergies, although he may get a different type of allergy than his folks. His chances of developing allergies rise as high as 60 to 80 percent if both parents have them. Still, children from the same family may not get the same allergies. Studies show that only 25 to 50 percent of identical twins share the same type of allergy.