Family background and age seem to be known causes of certain allergies. Hay fever, asthma, hives and eczema can be traced back to specific family backgrounds. While allergies such as milk, soy, wheat and eggs are considered to be more age related and occur mostly in children. In adults, food allergies are most commonly connected with the ingestion of peanuts, fish and shellfish.
Recent studies also suggest that an immune system defect may also cause food allergies. Dr. Claudio Nicoletti of the Institute of Food Research in the United Kingdom believes that an allergy happens in 2 stages. He explains that "There are two stages to food allergy. The first is sensitisation, when the immune system starts producing an antibody in response to eating a food. The second is when that food is eaten for a second time, triggering an allergic reaction. We have identified an immune response malfunction that occurs in the sensitisation stage, which could provide a target for future therapies," (qtd. in FoodQuality news.com)
Food Allergies are estimated to occur in 6 to 8 percent of infants and young children. A number of these children outgrow their Food Allergies over the first three to five years of life.