Impact of Vaccination on Th2 Immunity in Infancy

Inclusion Criteria: * Written informed consent from parent/guardian * General good health without other known need for blood draws that would conflict with the study volume requirements * Aged 5 months - 7 months, any race/ethnicity, any gender * Subjects must not have yet received their third DTaP vaccination, which typically is given at 6 months of age. Subjects must have previously received two doses of the DTaP vaccination, at ages 2 months and 4 months * Willingness to return for follow-up testing as defined in the protocol and consent if screening tests indicate eligibility * Group 1 participants must have all of the following: * A negative skin prick test to egg, milk, and peanut * A negative IgE to egg, milk, and peanut * Group 2 participants must have all of the following: * A positive family history of allergic disease * Atopic Dermatitis not requiring prescription medication * A positive IgE to milk, egg, and/or peanut If Group 1 enrollment is completed first, participants must have all of the following to be enrolled in Group 2: * A family history of atopy * Atopic dermatitis not requiring prescription medication If Group 2 enrollment is completed first, participants must have all of the following to be enrolled in Group 1: -No personal or family history of atopic disease Exclusion Criteria: * History of anemia requiring any treatment * Previous allergic reaction to any food, defined as itching, rash, hives, swelling, vomiting, diarrhea, sneezing, rhinorrhea, wheezing, breathing difficulty, or passing out immediately after food ingestion. * Evidence of non-IgE-mediated reaction to milk or soy (i.e. milk/soy protein intolerance) or evidence of food protein induced enterocolitis syndrome (FPIES) * Severe atopic dermatitis (liberally defined as requiring prescription medication) * Unable to obtain serum sample for determination of egg, milk and peanut IgE levels * Use of short-acting anti-histamines (diphenhydramine, etc.) more than one time within 3 days of skin testing or on the day of skin testing * Any history of intravenous or oral steroid medication * Known underlying immune defect/deficiency or bleeding disorder