The number of American children with food allergies increased 18 percent between 1997 and 2007. As of 2010, an estimated 6 to 8 percent of children have food allergies. The precise cause of food allergies in children is unknown. However, several causes have been proposed.

Immature Gastrointestinal Tract

For a food allergy to develop, the allergen (a particle to which a person becomes allergic) must reach the bloodstream, causing the immune system to over-react. Because infants have more permeable GI tracts and less efficient digestion than adults, in-tact allergens are more likely to reach the bloodstream and cause allergy.

Hygiene Hypothesis

Children who are raised on farms, in third-world countries, who live with older siblings or attend daycare are less likely to develop allergies. Scientists believe the less-developed immune systems of children raised in very clean environments may respond inappropriately to benign substances, leading to allergy.

Maternal Influence

High consumption rates of certain foods during gestation or breastfeeding may predispose a child to developing a food allergy. Overall, breastfeeding seems to be protective against all types of allergies.

Route of Allergen Exposure

If an allergen is placed directly on a cut or abraded skin, the child is more likely to become allergic than if the allergen is eaten or inhaled.

Genetic Factors

If parents or siblings have allergies, the child is more likely to be affected.

Conclusion

The cause of childhood allergies is likely due to a combination of factors. Fortunately, many children outgrow their allergies before they reach adulthood.

Source:

DrGreene.com: Allergy Prevention

MedlinePlus: Allergy

More Information:

Dictionary of Allergy and Immunology Terms