Food allergies develop when a person consumes or comes in contact with their allergen, and the immune system makes an antibody called immunoglobulin E, or IgE. IgE then circulates through the blood and attaches to immune cells called mast cells and basophils. This initial exposure does not cause an allergic reaction, however subsequent contact with the same allergen may allow previously created IgE antibodies to recognize it. This recognition then launches an immune response that can result in a severe allergic reaction. However, some people make IgE against a certain food without developing an allergy, and others still may develop only a mild allergy compared to those who experience severe reactions. Researchers are investigating why severe allergies develop in some people and whether this process can be avoided.
Investigators, including NIAID-funded researchers, have discovered several factors that can increase a person’s risk for developing food allergies. Those who already have a food allergy or another allergic disease are more likely than those who do not to develop food allergies. Young children are also more likely to develop food allergies compared with older children or adults. In 2014, NIAID-funded researchers discovered that the presence of some naturally-occurring gut bacteria may influence a person’s chance of developing food allergies.
Genetics are also likely to play a role. People who come from a family in which allergic diseases—such as food allergies, eczema, hay fever, or asthma—are common are more likely to develop food allergies. Likewise, a person with two allergic parents is even more likely to develop food allergy than someone with one allergic parent. Specifically, researchers working within the NIAID-sponsored Consortium for Food Allergy Research discovered genes that increase the risk for peanut allergy among European Americans.
NIAID-supported research not only illuminates factors that increase the risk of developing food allergy but also evaluates ways to prevent their onset. In February 2015, scientists reported results from the Learning Early About Peanut Allergy (LEAP) study, a large clinical trial conducted by the NIAID-funded Immune Tolerance Network. The goal of this trial was to determine whether early exposure to peanut-containing foods can prevent the development of peanut allergy. The study enrolled 640 children under a year of age thought to be at a high risk of developing peanut allergy because they had severe eczema, an allergy to egg, or both. These children were divided into two groups: one that avoided peanuts until they were five years old and one that immediately started eating peanut-containing foods at least three times per week until age five. When the children reached five years of age, the rate of peanut allergy was 80 percent lower in the group that had eaten peanut products compared to the group that had avoided them.
In March 2016, researchers reported results from a follow-up study that enrolled 274 LEAP participants who had regularly consumed peanut-containing foods from infancy to age 5, as well as 282 who had avoided peanut during the same period. The investigators asked both groups to avoid peanut consumption for one year. At age 6, the prevalence of peanut allergy was 74 percent lower among those whose early diet included peanut than among those who originally avoided peanut. These results suggest that the early introduction of peanut into one’s diet prevents, rather than delays, the development of peanut allergy and that the benefit is robust and lasting. A panel of experts convened by NIAID are working to incorporate the latest research into updated recommendations about introducing peanut-containing foods into the diet of infants and young children.