The purpose of this study is to observe the natural course of food allergy, including both the development of peanut allergy in infants at high risk for developing this allergy, and the resolution of both egg and cow's milk allergy.

The study will correlate biological markers and immunologic changes associated with the development of food allergy and the resolution of allergies to egg and cow's milk. It will also evaluate important genetic and environmental influences on these food allergies.

This observational study will investigate the developmental immunology of peanut, egg, and milk allergy in a cohort of milk- or egg-allergic children who are at risk for peanut allergy. This strategy will help to delineate, compare, and contrast biological markers and immunologic changes associated with the development of peanut allergy and loss of egg and milk allergy, while simultaneously evaluating important clinical and environmental influences likely to account for the recent rise in the prevalence of these allergies. The hallmark of food-allergic disease is the production of food-specific IgE antibodies that represent an end result of a Th2 influenced immune response. Currently, there is only a limited understanding of the mechanisms involved in the developmental course of food allergies. To effectively prevent or reverse the progression of food allergy, immune interventions will be needed. Furthermore, it is likely that successful strategies will need to be directed to those persons at identifiable risk (e.g., who have biomarkers associated with development of peanut allergy).

This study duration is planned for 5 years. There will be at least 7 study visits; at each study visit, medical, allergy, and diet history will be noted. At study entry, stool samples will be collected from infants and dust samples will be taken from their homes to assess for endotoxin and allergens in the home environment. At selected visits, participants will undergo a physical exam, atopic dermatitis and asthma evaluations, and blood collection. Oral food challenges will also occur at some visits, as clinically indicated. Infants will receive standard of care advice for treatment of egg, milk, and peanut allergy for the duration of the study.

In addition to the infants enrolled in this study, their full siblings will be asked to join the study as either genetic or mechanistic study controls, or both; controls will undergo allergy history at study entry. Siblings participating in genetic testing will have DNA collected by cheek swab; siblings participating in the mechanistic studies will have blood collected.

Inclusion Criteria for Children with Food Allergy:

• Have completed atopic dermatitis evaluation
• Clinical history of allergy to cow's milk or egg and positive skin prick test (3 mm or larger) to cow's milk or egg OR moderate to severe atopic dermatitis and a positive prick skin test to cow's milk or egg OR positive oral food challenge (prior to study entry) to either cow's milk or egg and a positive skin prick test to cow's milk or egg
• Parent or guardian willing to provide informed consent
• Peanut-specific IgE of 5 kIU/l or less at the time of enrollment (for 380 of 400 participants)
• Peanut-specific IgE of greater than 5 kIU/l at the time of enrollment (for 60 of 400 participants)

Exclusion Criteria for Children with Food Allergy:

• Chronic disease requiring therapy (e.g., heart disease, diabetes). Children with asthma, atopic dermatitis, or rhinitis are not excluded.
• Current participation in an interventional clinical trial
• Inability to discontinue antihistamines for routine tests
• Children from families with one child already participating in the study
• Confirmed or convincing evidence of peanut allergy

Inclusion Criteria for Siblings of Children with Food Allergy:

• Full sibling of child enrolled in the study
• Parent or guardian willing to provide informed consent/signed assent, if applicable

Exclusion Criteria for Siblings of Children with Food Allergy Participating in Mechanistic Study:

• History of food allergy
• History of asthma, atopic dermatitis, or allergic rhinitis
• History of chronic anemia
• Immune system disease or taking medication that impairs immune responses